I don't think OOC-ness is against the rules. A lot of prompts are crackfic for the purposes of humor, absurdity, or porn, so of course they are OOC. What is adamantly not allowed here is stuff that blurs lines about ethics. They don't want good characters like the Avengers being rapists, and they don't want evil characters being excused for their behavior. That's a consistently applied rule.

I know some people like Dark!Avengers and stuff, but there are other places to do it, and I kind of like the strong line that is taken here. It makes for an interesting community that is full of awful porn and awful jokes, but is also very accountable.