How much HTML can Charas handle?

[Grandy]

The title sums it up.
I've seen in other forums some tags to, let's say, change the background color or imbed music to a thread. Needless to say, they don't work in Charas, so I was wondering, how far is it possible to mess with it?

[game_maniac]

Well, in some cases if you let members get too wild with HTML, there's a good chance they can screw up a topic (or various).

[Grandy]

I know that, but still. There could be a rule against screwing up topics, unless in the Unmod.