Index: wp-content/themes/twentyeleven/colors/dark.css
===================================================================
--- wp-content/themes/twentyeleven/colors/dark.css	(revision 18965)
+++ wp-content/themes/twentyeleven/colors/dark.css	(working copy)
@@ -458,6 +458,11 @@
 .comment-meta {
 	color: #999;
 }
+.commentlist .avatar {
+	-webkit-box-shadow: 0 1px 2px #222;
+	-moz-box-shadow: 0 1px 2px #222;
+	box-shadow: 0 1px 2px #222;
+}
 a.comment-reply-link {
 	background: #242424;
 	color: #bbb;