It's pretty subjective. We're ultimately petty dictators, and don't always adhere to boring things like rules.
In general though, we frown upon excess creepiness (stalker behavior, explicit sexual innuendos involving another user, etc), flaming/trolling (to an extent), and pretty much anything else we dislike at the time.
We do have a bunch of bleeding heart liberal scumAcolytes who fight tooth and nail for the rights of users, so if you feel uncertain about something or wish for us to confer privately about an issue you are having on the boards or wish to plot La Revoluci?n, feel free to send one of them a PM.