Oh, the new layout is MUCH MUCH better - HulkSMASH desires are disipating rapidly. It's like being on a proper forum again.
If it wasn't you changing anything, then the magic happened when I clicked the "show unread messages since last visit" link on the sidebar.
Check out the Feats page on the wiki. Despite offering it as an option, and its effects showing up in the editing box in RTF mode, the actual displayed page doesn't accept the <h1>, <h2>, etc tags