Quite simply I have a common sense rule: You are not a child but if you act like one you won't be allowed to be on an adult board. Some of the following include childish behavior which is not allowed.
1) Racist/Sexist/Speciest comments not ICly done.
2) Slander/Harassment/Hexing/defamation of an individual or group in the real world.
3) Soliciting of unauthorized material including pirated/illegal/offensive subject matter.
There are no loopholes so just because it isn't specifically mentioned doesn't mean you can do it.