Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 23460)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -2306,7 +2306,7 @@
 }
 
 .sidebar .comment-list #reply-title,
-.sidebar .comment-list #commentform {
+.sidebar .comment-list #respond #commentform {
 	padding: 0;
 }