Literotica's a little vague, but CHYOO had a clearly defined list of story-related rules
buried in a story, while CHYOA has a nice page
dedicated to this subject on the bottom of the main page which apparently copies the CHYOO set in terms of content. Both specifically state no bestiality and extreme violence in addition to underage sex.
Around here, rape has been allowed, though usually in the context of either victim testimony (as opposed to colorful narration) or a victim who surrenders in order to survive and thereby pacifies the rapist to a certain degree. There are also a few chapters that feature fighting and someone dying, though they're no more graphic than a verbal adaptation of a boxing movie. We've also got a murder mystery story (that's been pretty much abandoned), so unless Friedman and Murakami have decided to crack down on this (which I doubt), I say it depends on how graphic you want to make these scenes.