Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21450)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -1169,6 +1169,7 @@
 	color: #21759b;
 }
 .commentlist .pingback {
+	line-height: 1.714285714;
 	margin-bottom: 24px;
 	margin-bottom: 1.714285714rem;
 }