Im sure they were first implemented with best intentions in mind but I've see them passed out so many times for no real reason other than just disagreeing with some mods opinion or just because someone was in a bad mood. They seem to be impossible to avoid and from what I've seen, the reasons vary from completely ridiculous (like using a non-offensive word or figure of speech some mod doesnt like or for mild sarcasm) to arbitrary reasons where it's not even clear why the poster got infracted at all.
Ive seen it happen far too many times when obvious vulgar language, name calling, bashing gets a free pass and then all of a sudden if someone disagrees with a popular opinion they get an infraction for calling someone stubborn, arrogant, stuck up etc. or saying something mildly sarcastic.
Another possible solution to this might be peer preview for breaking smaller rules. Mods are people too and make mistakes and they can get worked up and try to find reasons to pass out infractions and bans to people they disagree with or dont exactly like so another mods confirmation that the offense was actually infraction-worthy might make a lot of difference and avoid lots of problems later.
Otherwise, Im not really sure whats allowed or not. At least the rules don't say anything about sarcasm or having a different opinion than a mod.