Index: src/wp-includes/comment-template.php
===================================================================
--- src/wp-includes/comment-template.php	(revision 47548)
+++ src/wp-includes/comment-template.php	(working copy)
@@ -2250,6 +2250,7 @@
  *     @type string $id_submit            The comment submit element id attribute. Default 'submit'.
  *     @type string $class_form           The comment form element class attribute. Default 'comment-form'.
  *     @type string $class_submit         The comment submit element class attribute. Default 'submit'.
+ *     @type string $class_respond         The comment submit element class attribute. Default 'comment-respond'.
  *     @type string $name_submit          The comment submit element name attribute. Default 'submit'.
  *     @type string $title_reply          The translatable 'reply' button label. Default 'Leave a Reply'.
  *     @type string $title_reply_to       The translatable 'reply-to' button label. Default 'Leave a Reply to %s',
@@ -2378,7 +2379,7 @@
 	 * @param string[] $fields Array of the default comment fields.
 	 */
 	$fields = apply_filters( 'comment_form_default_fields', $fields );
-
+        
 	$defaults = array(
 		'fields'               => $fields,
 		'comment_field'        => sprintf(
@@ -2425,6 +2426,7 @@
 		'id_submit'            => 'submit',
 		'class_form'           => 'comment-form',
 		'class_submit'         => 'submit',
+                'class_respond'        => 'comment-respond',
 		'name_submit'          => 'submit',
 		'title_reply'          => __( 'Leave a Reply' ),
 		/* translators: %s: Author of the comment being replied to. */
@@ -2469,9 +2471,10 @@
 	 * @since 3.0.0
 	 */
 	do_action( 'comment_form_before' );
-	?>
-	<div id="respond" class="comment-respond">
-		<?php
+	printf(
+                '<div id="respond" class="%s">',
+                esc_attr( $args['class_respond'] )
+        );
 		echo $args['title_reply_before'];
 
 		comment_form_title( $args['title_reply'], $args['title_reply_to'] );
@@ -2661,8 +2664,9 @@
 			echo '</form>';
 
 		endif;
-		?>
-	</div><!-- #respond -->
+	echo '</div>';
+        ?>
+        <!-- #respond -->
 	<?php
 
 	/**