Yeah I tried that yesterday too before I asked the question. It would be a really cool feature to add to the forum but I don't want to start another jihad.
It was the gallery, not HTML, that caused the last one. The gallery was uber old and basically allowed you do to this:
* upload php script
* run php script
Why the execute permissions were not tighter is beyond me. But it was probably more or less an alpha-level gallery add-on that people used in good faith.
IMO the real downside is that I've seen boards with HTML turned on take on a circus feel after a while.
The board of directors is discussing it. We'll let you know what happens.