You won't be banned for occasional profanity, but the general suggestion is to keep things PG-13 at the very least. Slurs of any kind are out of the question, however, and those can quickly land you a Terms of Use violation (and subsequent ban).
Per Joupena, swearing itself is alright as long as you keep it civil and is not something we'd respond with a block. Directing profanity at others, using slurs, spamming profanity etc. is a different matter and of course aren't allowed.