Weirdly, I was just pondering exactly the same thing. I'm just compiling some recs, and was noticing one author used character, character rather than character/character. In this case I think it's because the sexual act is a non-consensual one, and it feels like over-dignifying it to use a slash.

I don't think we always and only use / for sex acts though. Certainly I've see pre-slash, slashy moments with no sex etc marked with a /, so as long as the dynamic is along those lines, I think you could go with it.