Most of the forums in the BigMooseSaloon don't let you post HTML, but you can use UbbCode, at least in some of the forums. Every time you post a new note, you will be told whether UBB Code is enabled for that particular forum. UBB Code is similar to HTML, but offers just a few basic functions, such as hyperlinking, image display, bolding and italicizing.
The code tag allows you to optionally specify several language types, and to specify a starting line number. For example, you could use a starting tag of [code=java:firstline] to force the language highlighting to match java keywords and conventions, and the code line numbers to start at line 1020.
In signatures, [i] and can be used; the others won't work in order to keep the signatures from becoming too distracting. That's also the reason why they can no longer contain raw HTML, and why we're asking members to keep them short (no more than 2 lines).