Ticket #21441: 21441-editor-body.diff

wp-content/themes/twentytwelve/editor-style-rtl.css

@@ -8 +8 @@
 html .mceContentBody {
         direction: rtl;
         unicode-bidi: embed;
-        float: right;
+        margin: 10px auto;
 }
 li {
         margin: 0 24px 0 0;