One other suggestion for you ;)
If there's no headers in the content and you therefore won't be generating anything, don't render the plugin at all.
Some pages on my site have sub-headings, others don't, so it only makes sense to display if there's something useful to show. I've done a basic hack for myself, but you might want to make it an option or something. Here's the code I put in -
The relevant code is the
if block on line 47.