The difference between the rules for downvotes and how they're actually used by users is one of the things that brought this to mind. Some forums specifically forbid complaining about downvotes, but even in fora where such complaints aren't specifically against the rules, they're still generally frowned upon, and that is expressed in downvotes. It's sort of like community rule enforcement: if enough people think a rule should be followed, they'll make their opinion known, even if it's not one of the written rules.