there are no hard and fast rules when it comes to interacting with people.

I think there is one, actually, which is: be consistent. At least then, those who interact with you regularly can learn your style and calibrate accordingly. Even on forums, you can look to one's commenting history to calibrate your reading of a comment with no other context. I've certainly done this, on occasions when some comment deviated significantly from the norm of polite discourse, usually to find that the commenter simply has a different norm than I expect.