Well, for starters, we usually give a warning. If a Mod tells you, either via PM or in public, not to do something, it's probably a VERY STUPID idea to argue with him. Guaranteed, he knows the rules, and their intent, better than you do. And don't try editorializing on what you see as heavy-handed moderation.
Angus' post closing POTNAC 9 was left in place so everyone could see just the kind of stupid thing that can get you in trouble. We've also left some examples of near-misses in place (where we could, and normally would, have banned the members in question), such as the post sequence that got POTNAC 10 closed. One of the concerned parties later apologized for a post that was wide open to misinterpretation.
Remember - POTNAC isn't the exclusive preserve of the active participants in the thread(s). GOOGLE actively searches POTN and can index a post within minutes. Pekka is very concerned that posts in POTN not draw the wrong kind of attention (one of the reasons for some of the "banned" words). Careless posting and taking the piss can do just that. It's our job to help keep it from happening. We can do that better, and more unobtrusively, with your cooperation. And remember that there's a big difference between being brash and being obnoxious, though there can be a very fine line between the two. Obnoxious will get you into trouble. You're on the world stage here; behave accordingly.