Unless a story filter is explicitly "what Tourguide (or whoever) likes", it's impossible to draw up criteria for what's not acceptable. No two people will agree exactly where the lines are.

I like non-con abuse, but only if the object is to break the victim to slavery (and it succeeds, but not too soon!) I like ingenious tortures and humiliations more than punch-and-kick violence. I can't stand situations that are too like real life, whether it's subordinates at work submitting to the boss to keep their jobs, or abused prisoners in Rwanda/Columbia/Iraq/wherever. But all these are just my tastes, and I couldn't claim they represented any kind of absolute principle.

The point of the story codes is to allow every style and subject on the Library, while letting people pick what they want to read. I can't think of a better system.