diff --git a/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php b/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php
index e0384715acc..d5610f3e3f1 100644
--- a/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php
+++ b/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php
@@ -32,7 +32,7 @@ use Drupal\Core\Template\Attribute;
 class DateTimeDefaultFormatter extends FormatterBase {
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
 
@@ -93,7 +93,7 @@ class DateTimeDefaultFormatter extends FormatterBase {
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
 
@@ -119,15 +119,13 @@ class DateTimeDefaultFormatter extends FormatterBase {
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-
+    $summary = array();
     $date = new DrupalDateTime();
-    $output = array();
-    $output[] = t('Format: @display', array('@display' => $this->dateFormat($date, FALSE)));
-    return implode('<br />', $output);
-
+    $summary[] = t('Format: @display', array('@display' => $this->dateFormat($date, FALSE)));
+    return $summary;
   }
 
 }
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceEntityFormatter.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceEntityFormatter.php
index d829cb24c91..647de082839 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceEntityFormatter.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceEntityFormatter.php
@@ -33,7 +33,7 @@ use Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase;
 class EntityReferenceEntityFormatter extends EntityReferenceFormatterBase {
 
   /**
-   * Overrides \Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $view_modes = entity_get_view_modes($this->field['settings']['target_type']);
@@ -60,7 +60,7 @@ class EntityReferenceEntityFormatter extends EntityReferenceFormatterBase {
   }
 
   /**
-   * Overrides \Drupal\field\Plugin\Type\Formatter\FormatterBase::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
     $summary = array();
@@ -70,11 +70,11 @@ class EntityReferenceEntityFormatter extends EntityReferenceFormatterBase {
     $summary[] = t('Rendered as @mode', array('@mode' => isset($view_modes[$view_mode]['label']) ? $view_modes[$view_mode]['label'] : $view_mode));
     $summary[] = $this->getSetting('links') ? t('Display links') : t('Do not display links');
 
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
-   * Overrides \Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     // Remove un-accessible items.
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceLabelFormatter.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceLabelFormatter.php
index 426aa979f92..499edc70d14 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceLabelFormatter.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceLabelFormatter.php
@@ -31,7 +31,7 @@ use Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase;
 class EntityReferenceLabelFormatter extends EntityReferenceFormatterBase {
 
   /**
-   * Overrides \Drupal\field\Plugin\Type\Formatter\FormatterBase::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $elements['link'] = array(
@@ -44,17 +44,16 @@ class EntityReferenceLabelFormatter extends EntityReferenceFormatterBase {
   }
 
   /**
-   * Overrides \Drupal\field\Plugin\Type\Formatter\FormatterBase::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
     $summary = array();
     $summary[] = $this->getSetting('link') ? t('Link to the referenced entity') : t('No link');
-
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
-   * Overrides \Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     // Remove un-accessible items.
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterBase.php
index a46b4658878..6b316aec657 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterBase.php
@@ -78,7 +78,7 @@ abstract class FormatterBase extends PluginSettingsBase implements FormatterInte
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::view().
+   * {@inheritdoc}
    */
   public function view(EntityInterface $entity, $langcode, array $items) {
     $field = $this->field;
@@ -113,21 +113,21 @@ abstract class FormatterBase extends PluginSettingsBase implements FormatterInte
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     return array();
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-    return '';
+    return array();
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::prepareView().
+   * {@inheritdoc}
    */
   public function prepareView(array $entities, $langcode, array &$items) { }
 
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterInterface.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterInterface.php
index 907cf0b4034..8f7f3dfee8f 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterInterface.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterInterface.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\field\Plugin\Type\Formatter\FormatterInterface.
+ * Contains \Drupal\field\Plugin\Type\Formatter\FormatterInterface.
  */
 
 namespace Drupal\field\Plugin\Type\Formatter;
@@ -40,8 +40,8 @@ interface FormatterInterface extends PluginSettingsInterface {
    * configurable settings, and no UI will be provided to display a settings
    * form.
    *
-   * @return string
-   *   A short summary of the formatter settings..
+   * @return array()
+   *   A short summary of the formatter settings.
    */
   public function settingsSummary();
 
diff --git a/core/modules/field/tests/modules/field_test/field_test.module b/core/modules/field/tests/modules/field_test/field_test.module
index 15b3ea5873a..33623bf3d41 100644
--- a/core/modules/field/tests/modules/field_test/field_test.module
+++ b/core/modules/field/tests/modules/field_test/field_test.module
@@ -276,7 +276,8 @@ function field_test_field_formatter_settings_form_alter(&$element, &$form_state,
  * Implements hook_field_formatter_settings_summary_alter().
  */
 function field_test_field_formatter_settings_summary_alter(&$summary, $context) {
-  $summary .= '<br />field_test_field_formatter_settings_summary_alter';
+  $summary[] = 'field_test_field_formatter_settings_summary_alter';
+  return $summary;
 }
 
 /**
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldDefaultFormatter.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldDefaultFormatter.php
index 460936395bb..a42ea78941b 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldDefaultFormatter.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldDefaultFormatter.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\field_test\Plugin\field\formatter\TestFieldDefaultFormatter.
+ * Contains \Drupal\field_test\Plugin\field\formatter\TestFieldDefaultFormatter.
  */
 
 namespace Drupal\field_test\Plugin\field\formatter;
@@ -31,7 +31,7 @@ use Drupal\Core\Entity\EntityInterface;
 class TestFieldDefaultFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $element['test_formatter_setting'] = array(
@@ -45,14 +45,16 @@ class TestFieldDefaultFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-    return t('@setting: @value', array('@setting' => 'test_formatter_setting', '@value' => $this->getSetting('test_formatter_setting')));
+    $summary = array();
+    $summary[] = t('@setting: @value', array('@setting' => 'test_formatter_setting', '@value' => $this->getSetting('test_formatter_setting')));
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldMultipleFormatter.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldMultipleFormatter.php
index bca03956892..f2aad3b0660 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldMultipleFormatter.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldMultipleFormatter.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\field_test\Plugin\field\formatter\TestFieldMultipleFormatter.
+ * Contains \Drupal\field_test\Plugin\field\formatter\TestFieldMultipleFormatter.
  */
 
 namespace Drupal\field_test\Plugin\field\formatter;
@@ -31,7 +31,7 @@ use Drupal\Core\Entity\EntityInterface;
 class TestFieldMultipleFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $element['test_formatter_setting_multiple'] = array(
@@ -45,14 +45,16 @@ class TestFieldMultipleFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-    return t('@setting: @value', array('@setting' => 'test_formatter_setting_multiple', '@value' => $this->getSetting('test_formatter_setting_multiple')));
+    $summary = array();
+    $summary[] = t('@setting: @value', array('@setting' => 'test_formatter_setting_multiple', '@value' => $this->getSetting('test_formatter_setting_multiple')));
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldPrepareViewFormatter.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldPrepareViewFormatter.php
index 6796143d429..8e6ad38fa27 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldPrepareViewFormatter.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldPrepareViewFormatter.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\field_test\Plugin\field\formatter\TestFieldPrepareViewFormatter.
+ * Contains \Drupal\field_test\Plugin\field\formatter\TestFieldPrepareViewFormatter.
  */
 
 namespace Drupal\field_test\Plugin\field\formatter;
@@ -31,7 +31,7 @@ use Drupal\Core\Entity\EntityInterface;
 class TestFieldPrepareViewFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $element['test_formatter_setting_additional'] = array(
@@ -45,14 +45,16 @@ class TestFieldPrepareViewFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-    return t('@setting: @value', array('@setting' => 'test_formatter_setting_additional', '@value' => $this->getSetting('test_formatter_setting_additional')));
+    $summary = array();
+    $summary[] = t('@setting: @value', array('@setting' => 'test_formatter_setting_additional', '@value' => $this->getSetting('test_formatter_setting_additional')));
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::prepareView().
+   * {@inheritdoc}
    */
   public function prepareView(array $entities, $langcode, array &$items) {
     foreach ($items as $id => $item) {
@@ -66,7 +68,7 @@ class TestFieldPrepareViewFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/field_ui/field_ui.api.php b/core/modules/field_ui/field_ui.api.php
index ff25ad59ca3..81a5f3bffd9 100644
--- a/core/modules/field_ui/field_ui.api.php
+++ b/core/modules/field_ui/field_ui.api.php
@@ -93,10 +93,10 @@ function hook_field_instance_settings_form($field, $instance, $form_state) {
 }
 
 /**
- * Alter the formatter settings form.
+ * Alters the formatter settings form.
  *
  * @param $element
- *   Form array as returned by hook_field_formatter_settings_form().
+ *   Form array.
  * @param $form_state
  *   The form state of the (entire) configuration form.
  * @param $context
@@ -106,6 +106,8 @@ function hook_field_instance_settings_form($field, $instance, $form_state) {
  *   - instance: The instance structure being configured.
  *   - view_mode: The view mode being configured.
  *   - form: The (entire) configuration form array.
+ *
+ * @see \Drupal\field_ui\DisplayOverView.
  */
 function hook_field_formatter_settings_form_alter(&$element, &$form_state, $context) {
   // Add a 'mysetting' checkbox to the settings form for 'foo_field' fields.
@@ -119,23 +121,25 @@ function hook_field_formatter_settings_form_alter(&$element, &$form_state, $cont
 }
 
 /**
- * Alter the field formatter settings summary.
+ * Alters the field formatter settings summary.
  *
  * @param $summary
- *   The summary as returned by hook_field_formatter_settings_summary().
+ *   The summary.
  * @param $context
  *   An associative array with the following elements:
  *   - formatter: The formatter object.
  *   - field: The field structure being configured.
  *   - instance: The instance structure being configured.
  *   - view_mode: The view mode being configured.
+ *
+ * @see \Drupal\field_ui\DisplayOverView.
  */
 function hook_field_formatter_settings_summary_alter(&$summary, $context) {
   // Append a message to the summary when an instance of foo_field has
   // mysetting set to TRUE for the current view mode.
   if ($context['field']['type'] == 'foo_field') {
     if ($context['formatter']->getSetting('mysetting')) {
-      $summary .= '<br />' . t('My setting enabled.');
+      $summary[] = t('My setting enabled.');
     }
   }
 }
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php b/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
index f8c440b96b5..c1a490d6f19 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
@@ -265,9 +265,9 @@ class DisplayOverview extends OverviewBase {
           );
           drupal_alter('field_formatter_settings_summary', $summary, $context);
 
-          if ($summary) {
+          if (!empty($summary)) {
             $table[$name]['settings_summary'] = array(
-              '#markup' => '<div class="field-formatter-summary">' . $summary . '</div>',
+              '#markup' => '<div class="field-formatter-summary">' . implode('<br />', $summary) . '</div>',
               '#cell_attributes' => array('class' => array('field-formatter-summary-cell')),
             );
             $table[$name]['settings_edit'] = $base_button + array(
diff --git a/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatter.php b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatter.php
index de0503fe3c5..3edb7513c2c 100644
--- a/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatter.php
+++ b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatter.php
@@ -31,7 +31,7 @@ use Drupal\Core\Entity\EntityInterface;
 class ImageFormatter extends FormatterBase {
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $image_styles = image_style_options(FALSE);
@@ -59,7 +59,7 @@ class ImageFormatter extends FormatterBase {
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
     $summary = array();
@@ -87,11 +87,11 @@ class ImageFormatter extends FormatterBase {
       $summary[] = $link_types[$image_link_setting];
     }
 
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkFormatter.php b/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkFormatter.php
index b71f17e3727..123ededdc65 100644
--- a/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkFormatter.php
+++ b/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkFormatter.php
@@ -109,7 +109,7 @@ class LinkFormatter extends FormatterBase {
       $summary[] = t('Open link in new window');
     }
 
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
diff --git a/core/modules/number/lib/Drupal/number/Plugin/field/formatter/DefaultNumberFormatter.php b/core/modules/number/lib/Drupal/number/Plugin/field/formatter/DefaultNumberFormatter.php
index 55692603d24..86b4aa1ff00 100644
--- a/core/modules/number/lib/Drupal/number/Plugin/field/formatter/DefaultNumberFormatter.php
+++ b/core/modules/number/lib/Drupal/number/Plugin/field/formatter/DefaultNumberFormatter.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\number\Plugin\field\formatter\DefaultNumberFormatter.
+ * Contains \Drupal\number\Plugin\field\formatter\DefaultNumberFormatter.
  */
 
 namespace Drupal\number\Plugin\field\formatter;
@@ -18,7 +18,7 @@ use Drupal\Core\Entity\EntityInterface;
 abstract class DefaultNumberFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $options = array(
@@ -48,7 +48,7 @@ abstract class DefaultNumberFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
     $summary = array();
@@ -58,11 +58,11 @@ abstract class DefaultNumberFormatter extends FormatterBase {
       $summary[] = t('Display with prefix and suffix.');
     }
 
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php b/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php
index 37e034769ea..c235b08f860 100644
--- a/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php
+++ b/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\picture\Plugin\field\formatter\PictureFormatter.
+ * Contains \Drupal\picture\Plugin\field\formatter\PictureFormatter.
  */
 
 namespace Drupal\picture\Plugin\field\formatter;
@@ -32,7 +32,7 @@ use Drupal\Core\Entity\EntityInterface;
 class PictureFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $picture_options = array();
@@ -78,7 +78,7 @@ class PictureFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
     $summary = array();
@@ -109,11 +109,11 @@ class PictureFormatter extends FormatterBase {
       $summary[] = t('Select a picture mapping.');
     }
 
-    return implode('<br />', $summary);
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();
diff --git a/core/modules/telephone/lib/Drupal/telephone/Plugin/field/formatter/TelephoneLinkFormatter.php b/core/modules/telephone/lib/Drupal/telephone/Plugin/field/formatter/TelephoneLinkFormatter.php
index e7361121c5d..a8de9268cf8 100644
--- a/core/modules/telephone/lib/Drupal/telephone/Plugin/field/formatter/TelephoneLinkFormatter.php
+++ b/core/modules/telephone/lib/Drupal/telephone/Plugin/field/formatter/TelephoneLinkFormatter.php
@@ -30,7 +30,7 @@ use Drupal\Core\Entity\EntityInterface;
 class TelephoneLinkFormatter extends FormatterBase {
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $elements['title'] = array(
@@ -43,23 +43,24 @@ class TelephoneLinkFormatter extends FormatterBase {
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
+    $summary = array();
     $settings = $this->getSettings();
 
     if (!empty($settings['title'])) {
-      $summary = t('Link using text: @title', array('@title' => $settings['title']));
+      $summary[] = t('Link using text: @title', array('@title' => $settings['title']));
     }
     else {
-      $summary = t('Link using provided telephone number.');
+      $summary[] = t('Link using provided telephone number.');
     }
 
     return $summary;
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::prepareView().
+   * {@inheritdoc}
    */
   public function prepareView(array $entities, $langcode, array &$items) {
     $settings = $this->getSettings();
@@ -79,7 +80,7 @@ class TelephoneLinkFormatter extends FormatterBase {
   }
 
   /**
-   * Implements \Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $element = array();
diff --git a/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextTrimmedFormatter.php b/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextTrimmedFormatter.php
index ba8b417da5b..4be366d7839 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextTrimmedFormatter.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextTrimmedFormatter.php
@@ -3,7 +3,7 @@
 /**
  * @file
  *
- * Definition of Drupal\text\Plugin\field\formatter\TextTrimmedFormatter.
+ * Contains \Drupal\text\Plugin\field\formatter\TextTrimmedFormatter.
  */
 namespace Drupal\text\Plugin\field\formatter;
 
@@ -40,7 +40,7 @@ use Drupal\Core\Entity\EntityInterface;
 class TextTrimmedFormatter extends FormatterBase {
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state) {
     $element['trim_length'] = array(
@@ -54,16 +54,16 @@ class TextTrimmedFormatter extends FormatterBase {
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsSummary().
+   * {@inheritdoc}
    */
   public function settingsSummary() {
-    return t('Trim length: @trim_length', array(
-      '@trim_length' => $this->getSetting('trim_length'),
-    ));
+    $summary = array();
+    $summary[] = t('Trim length: @trim_length', array('@trim_length' => $this->getSetting('trim_length')));
+    return $summary;
   }
 
   /**
-   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   * {@inheritdoc}
    */
   public function viewElements(EntityInterface $entity, $langcode, array $items) {
     $elements = array();