Index: twentyeleven/header.php
===================================================================
--- twentyeleven/header.php	(revision 18619)
+++ twentyeleven/header.php	(working copy)
@@ -55,7 +55,7 @@
 	/* We add some JavaScript to pages with the comment form
 	 * to support sites with threaded comments (when in use).
 	 */
-	if ( is_singular() && get_option( 'thread_comments' ) )
+	if ( is_singular() && get_option( 'thread_comments' ) && comments_open() )
 		wp_enqueue_script( 'comment-reply' );
 
 	/* Always have wp_head() just before the closing </head>