Can I use profanity in questions, answers, or comments?
Sometimes I just really want to let loose and let my frustration show, and cussin' seems to be the best way to do it.
Expletives are not acceptable behavior on meta or any other Stack Overflow site. If you can't effectively communicate what you need to say without resorting to lowest common denominator cursing, then keep it to yourself.
If you use expletives, you will get a warning.
If you continue to use expletives, you will be placed on timed suspension.
While Jeff has left Stack Exchange this is still official policy.
It would also be considered a violation of the Be Nice policy 1. I would suggest that profanity, especially if directed at someone, falls under "Rudeness and belittling language", while run-of-the-mill "blue" language just in general is covered under "Don't be a jerk - Inappropriate language or attention". ("Vulgar terms" is specifically called out.)