There is a time and a place for everything. Just like real life.
Depending on the context of your reply if its ok or not. If your just bluntly swearing at a guy for no good mean reason, or your spamming cusswords just to be a prick then of course its not ok.
Rules are only needed for people that have no common sense.
If you are asking for a black and white answer about if you could cuss or not, then your to immature to be trying anyways.