This guy's bio contains the following:
programmers.SE, where 2/3 of all questions are summarily closed.
Why am I here? I like to piss off twits. Does that make you mad?
What do we do with that? That is trolling in my opinion...
I went browsing Meta SO for any profile rules, and it appears there really aren't any. A user's profile is a reflection of the user, not a reflection of the site.
You can put pretty much anything in there, even profanity, although since it is a reflection of the you, you may want to consider carefully what you put in there.
Generally speaking, your profile is (to an extent) fair game, as it is a reflection of you as a person, not the site as a whole.
Self-promotion, your e-mail address, humor, (if you know HTML) imagery and even the f-bomb are allowed there.
There are reasonable limitations for all of those, but generally speaking, unless you're a hard-core spammer or you put something truly offensive / crazy in there (like hate speech or pornography), you'll be OK.