I've been here since 2007 and I've been given only one warning. And I deserved the warning too. I don't think what I had done was all that bad, but it was listed in the Code of Conduct as a no-no and I'd forgotten. Any way you slice it, that's my fault. Warning given, lesson learned.
I'm not sure what bans or suspensions you're talking about specifically, but I find that if you're generally respectful and keep your wits about you then there shouldn't be any issues.
As a general rule of thumb, I'd say preview any post you make before you click "POST". Ask yourself how you would feel if a stranger walked up and said those things to you. If the answer is "That would tick me off", maybe reword your thoughts. If the answer is "I'd be ok with this being said to me", then you shouldn't run into too many problems. Again, that's just a generalized thought rather than a rule, but it's worked well for me.