diff --git a/core/modules/comment/comment-rtl.css b/core/modules/comment/comment-rtl.css
deleted file mode 100644
index 39c3929..0000000
--- a/core/modules/comment/comment-rtl.css
+++ /dev/null
@@ -1,5 +0,0 @@
-
-.indented {
-  margin-left: 0;
-  margin-right: 25px;
-}
diff --git a/core/modules/comment/comment.css b/core/modules/comment/comment.css
deleted file mode 100644
index a55f527..0000000
--- a/core/modules/comment/comment.css
+++ /dev/null
@@ -1,13 +0,0 @@
-
-#comments {
-  margin-top: 15px;
-}
-.indented {
-  margin-left: 25px; /* LTR */
-}
-.comment-unpublished {
-  background-color: #fff4f4;
-}
-.comment-preview {
-  background-color: #ffffea;
-}
diff --git a/core/modules/comment/comment.info b/core/modules/comment/comment.info
index db6dc2c..6bbd275 100644
--- a/core/modules/comment/comment.info
+++ b/core/modules/comment/comment.info
@@ -9,4 +9,4 @@ dependencies[] = entity
 files[] = comment.entity.inc
 files[] = comment.test
 configure = admin/content/comment
-stylesheets[all][] = comment.css
+stylesheets[all][] = comment.theme.css
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 9ad7cfc..d7638e6 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -2150,10 +2150,10 @@ function template_preprocess_comment(&$variables) {
 
   // Set status to a string representation of comment->status.
   if (isset($comment->in_preview)) {
-    $variables['status'] = 'comment-preview';
+    $variables['status'] = 'preview';
   }
   else {
-    $variables['status'] = ($comment->status == COMMENT_NOT_PUBLISHED) ? 'comment-unpublished' : 'comment-published';
+    $variables['status'] = ($comment->status == COMMENT_NOT_PUBLISHED) ? 'unpublished' : 'published';
   }
 
   // Gather comment classes.
@@ -2163,17 +2163,17 @@ function template_preprocess_comment(&$variables) {
     $variables['classes_array'][] = $variables['status'];
   }
   if ($variables['new']) {
-    $variables['classes_array'][] = 'comment-new';
+    $variables['classes_array'][] = 'new';
   }
   if (!$comment->uid) {
-    $variables['classes_array'][] = 'comment-by-anonymous';
+    $variables['classes_array'][] = 'by-anonymous';
   }
   else {
     if ($comment->uid == $variables['node']->uid) {
-      $variables['classes_array'][] = 'comment-by-node-author';
+      $variables['classes_array'][] = 'by-node-author';
     }
     if ($comment->uid == $variables['user']->uid) {
-      $variables['classes_array'][] = 'comment-by-viewer';
+      $variables['classes_array'][] = 'by-viewer';
     }
   }
 }
diff --git a/core/modules/comment/comment.test b/core/modules/comment/comment.test
index 74f735d..fd65776 100644
--- a/core/modules/comment/comment.test
+++ b/core/modules/comment/comment.test
@@ -525,56 +525,56 @@ class CommentInterfaceTest extends CommentHelperCase {
 
       // Verify classes if the comment is visible for the current user.
       if ($case['comment_status'] == COMMENT_PUBLISHED || $case['user'] == 'admin') {
-        // Verify the comment-by-anonymous class.
-        $comments = $this->xpath('//*[contains(@class, "comment-by-anonymous")]');
+        // Verify the by-anonymous class.
+        $comments = $this->xpath('//*[contains(@class, "by-anonymous")]');
         if ($case['comment_uid'] == 0) {
-          $this->assertTrue(count($comments) == 1, 'comment-by-anonymous class found.');
+          $this->assertTrue(count($comments) == 1, 'by-anonymous class found.');
         }
         else {
-          $this->assertFalse(count($comments), 'comment-by-anonymous class not found.');
+          $this->assertFalse(count($comments), 'by-anonymous class not found.');
         }
 
-        // Verify the comment-by-node-author class.
-        $comments = $this->xpath('//*[contains(@class, "comment-by-node-author")]');
+        // Verify the by-node-author class.
+        $comments = $this->xpath('//*[contains(@class, "by-node-author")]');
         if ($case['comment_uid'] > 0 && $case['comment_uid'] == $case['node_uid']) {
-          $this->assertTrue(count($comments) == 1, 'comment-by-node-author class found.');
+          $this->assertTrue(count($comments) == 1, 'by-node-author class found.');
         }
         else {
-          $this->assertFalse(count($comments), 'comment-by-node-author class not found.');
+          $this->assertFalse(count($comments), 'by-node-author class not found.');
         }
 
-        // Verify the comment-by-viewer class.
-        $comments = $this->xpath('//*[contains(@class, "comment-by-viewer")]');
+        // Verify the by-viewer class.
+        $comments = $this->xpath('//*[contains(@class, "by-viewer")]');
         if ($case['comment_uid'] > 0 && $case['comment_uid'] == $case['user_uid']) {
-          $this->assertTrue(count($comments) == 1, 'comment-by-viewer class found.');
+          $this->assertTrue(count($comments) == 1, 'by-viewer class found.');
         }
         else {
-          $this->assertFalse(count($comments), 'comment-by-viewer class not found.');
+          $this->assertFalse(count($comments), 'by-viewer class not found.');
         }
       }
 
-      // Verify the comment-unpublished class.
-      $comments = $this->xpath('//*[contains(@class, "comment-unpublished")]');
+      // Verify the unpublished class.
+      $comments = $this->xpath('//*[contains(@class, "unpublished")]');
       if ($case['comment_status'] == COMMENT_NOT_PUBLISHED && $case['user'] == 'admin') {
-        $this->assertTrue(count($comments) == 1, 'comment-unpublished class found.');
+        $this->assertTrue(count($comments) == 1, 'unpublished class found.');
       }
       else {
-        $this->assertFalse(count($comments), 'comment-unpublished class not found.');
+        $this->assertFalse(count($comments), 'unpublished class not found.');
       }
 
-      // Verify the comment-new class.
+      // Verify the new class.
       if ($case['comment_status'] == COMMENT_PUBLISHED || $case['user'] == 'admin') {
-        $comments = $this->xpath('//*[contains(@class, "comment-new")]');
+        $comments = $this->xpath('//*[contains(@class, "new")]');
         if ($case['user'] != 'anonymous') {
-          $this->assertTrue(count($comments) == 1, 'comment-new class found.');
+          $this->assertTrue(count($comments) == 1, 'new class found.');
 
-          // Request the node again. The comment-new class should disappear.
+          // Request the node again. The new class should disappear.
           $this->drupalGet('node/' . $node->nid);
-          $comments = $this->xpath('//*[contains(@class, "comment-new")]');
-          $this->assertFalse(count($comments), 'comment-new class not found.');
+          $comments = $this->xpath('//*[contains(@class, "new")]');
+          $this->assertFalse(count($comments), 'new class not found.');
         }
         else {
-          $this->assertFalse(count($comments), 'comment-new class not found.');
+          $this->assertFalse(count($comments), 'new class not found.');
         }
       }
     }
diff --git a/core/modules/comment/comment.theme-rtl.css b/core/modules/comment/comment.theme-rtl.css
new file mode 100644
index 0000000..c121023
--- /dev/null
+++ b/core/modules/comment/comment.theme-rtl.css
@@ -0,0 +1,13 @@
+
+/**
+ * @file
+ * RTL styles for comment module.
+ */
+
+/**
+ * Indent threaded comments.
+ */
+.indented {
+  margin-left: 0;
+  margin-right: 25px;
+}
diff --git a/core/modules/comment/comment.theme.css b/core/modules/comment/comment.theme.css
new file mode 100644
index 0000000..6a32a63
--- /dev/null
+++ b/core/modules/comment/comment.theme.css
@@ -0,0 +1,12 @@
+
+/**
+ * @file
+ * Basic styling for comment module.
+ */
+
+/**
+ * Indent threaded comments.
+ */
+.indented {
+  margin-left: 25px; /* LTR */
+}
diff --git a/core/modules/comment/comment.tpl.php b/core/modules/comment/comment.tpl.php
index 678f798..9232403 100644
--- a/core/modules/comment/comment.tpl.php
+++ b/core/modules/comment/comment.tpl.php
@@ -23,21 +23,20 @@
  * - $user_picture: The comment author's picture from user-picture.tpl.php.
  * - $signature: Authors signature.
  * - $status: Comment status. Possible values are:
- *   comment-unpublished, comment-published or comment-preview.
+ *   unpublished, published or preview.
  * - $title: Linked title.
  * - $classes: String of classes that can be used to style contextually through
  *   CSS. It can be manipulated through the variable $classes_array from
  *   preprocess functions. The default values can be one or more of the
  *   following:
  *   - comment: The current template type, i.e., "theming hook".
- *   - comment-by-anonymous: Comment by an unregistered user.
- *   - comment-by-node-author: Comment by the author of the parent node.
- *   - comment-preview: When previewing a new or edited comment.
+ *   - by-anonymous: Comment by an unregistered user.
+ *   - by-node-author: Comment by the author of the parent node.
+ *   - preview: When previewing a new or edited comment.
  *   The following applies only to viewers who are registered users:
- *   - comment-unpublished: An unpublished comment visible only to
- *     administrators.
- *   - comment-by-viewer: Comment by the user currently viewing the page.
- *   - comment-new: New comment since last the visit.
+ *   - unpublished: An unpublished comment visible only to administrators.
+ *   - by-viewer: Comment by the user currently viewing the page.
+ *   - new: New comment since last the visit.
  * - $title_prefix (array): An array containing additional output populated by
  *   modules, intended to be displayed in front of the main title tag that
  *   appears in the template.
diff --git a/core/themes/bartik/css/style-rtl.css b/core/themes/bartik/css/style-rtl.css
index 48f64ab..789b9ca 100644
--- a/core/themes/bartik/css/style-rtl.css
+++ b/core/themes/bartik/css/style-rtl.css
@@ -1,4 +1,3 @@
-
 /* ------------------ Reset Styles ------------------ */
 
 caption,
@@ -125,7 +124,7 @@ ul.tips {
 .comment ul.links li {
   padding: 0 0 0.5em;
 }
-.comment-unpublished {
+.comment.unpublished {
   margin-left: 5px;
   margin-right: 0;
   padding: 5px 5px 5px 2px;
diff --git a/core/themes/bartik/css/style.css b/core/themes/bartik/css/style.css
index 850a69c..057471a 100644
--- a/core/themes/bartik/css/style.css
+++ b/core/themes/bartik/css/style.css
@@ -1,4 +1,3 @@
-
 /* ---------- Overall Specifications ---------- */
 
 body {
@@ -726,11 +725,11 @@ ul.links {
 .comment ul.links li {
   padding: 0 0.5em 0 0; /* LTR */
 }
-.comment-unpublished {
+.comment.unpublished {
   margin-right: 5px; /* LTR */
   padding: 5px 2px 5px 5px; /* LTR */
 }
-.comment-unpublished .comment-text .comment-arrow {
+.comment.unpublished .comment-text .comment-arrow {
   border-left: 1px solid #fff4f4;
   border-right: 1px solid #fff4f4;
 }
diff --git a/core/themes/bartik/templates/comment.tpl.php b/core/themes/bartik/templates/comment.tpl.php
index 553fb53..181295e 100644
--- a/core/themes/bartik/templates/comment.tpl.php
+++ b/core/themes/bartik/templates/comment.tpl.php
@@ -23,19 +23,19 @@
  * - $picture: Authors picture.
  * - $signature: Authors signature.
  * - $status: Comment status. Possible values are:
- *   comment-unpublished, comment-published or comment-preview.
+ *   unpublished, published or preview.
  * - $title: Linked title.
  * - $classes: String of classes that can be used to style contextually through
  *   CSS. It can be manipulated through the variable $classes_array from
  *   preprocess functions. The default values can be one or more of the following:
  *   - comment: The current template type, i.e., "theming hook".
- *   - comment-by-anonymous: Comment by an unregistered user.
- *   - comment-by-node-author: Comment by the author of the parent node.
- *   - comment-preview: When previewing a new or edited comment.
+ *   - by-anonymous: Comment by an unregistered user.
+ *   - by-node-author: Comment by the author of the parent node.
+ *   - preview: When previewing a new or edited comment.
  *   The following applies only to viewers who are registered users:
- *   - comment-unpublished: An unpublished comment visible only to administrators.
- *   - comment-by-viewer: Comment by the user currently viewing the page.
- *   - comment-new: New comment since last the visit.
+ *   - unpublished: An unpublished comment visible only to administrators.
+ *   - by-viewer: Comment by the user currently viewing the page.
+ *   - new: New comment since last the visit.
  * - $title_prefix (array): An array containing additional output populated by
  *   modules, intended to be displayed in front of the main title tag that
  *   appears in the template.