diff --git a/modules/comment/comment.module b/modules/comment/comment.module
index 865b4560f50..7445ca6186e 100644
--- a/modules/comment/comment.module
+++ b/modules/comment/comment.module
@@ -1545,9 +1545,15 @@ function _comment_form_submit($form_values) {
     // 1) Filter it into HTML
     // 2) Strip out all HTML tags
     // 3) Convert entities back to plain-text.
-  // Note: format is checked by check_markup().
-    $form_values['subject'] = truncate_utf8(decode_entities(strip_tags(check_markup($form_values['comment'], $form_values['format']))), 29, TRUE);
+    // Note: format is checked by check_markup().
+    $form_values['subject'] = trim(truncate_utf8(decode_entities(strip_tags(check_markup($form_values['comment'], $form_values['format']))), 29, TRUE));
+    // Edge cases where the comment body is populated only by HTML tags will
+    // require a default subject.
+    if ($form_values['subject'] == '') {
+      $form_values['subject'] = t('(No subject)');
+    }
   }
+
   return $form_values;
 }