bbcode is currently usable in signatures and posts. if you input bad bbcode, like
[raw][b]words words[/i][/raw], it will tell you it's bad. and that's about all. I'll get to error messages shortly; it was enough of a pain just checking to see if the code's right.
anyway, the tags you can use are:
[b]:
bold[i]:
italic[u]:
underline[s]:
strike-through[color=xxx]:
change color, which I'm sure will be highly abused
[url]:
link; either as [url=URL]TEXT[/url] or [url]URL[/url]
[img]: image; either as [img=URL]ALT TEXT[/img] or [img]URL[/img]
[code]: big phpbb-style code block
[mono]: inline
monospace text
[hr]: horizontal rule; there is NO END TAG
there is also a [raw] tag that will prevent its contents from being treated as bbcode. if you want to write a closing [/raw] tag, well, you'll have to be a little creative.
I plan to add sizes and lists and maybe even tables later, but they are a little more complicated than the above.
bug reports welcome.