I don't follow the genre, but I heard that apparently Steam is also very inconsistent in terms of banning visual novels. And the fans seem to be pretty dedicated to them, so you have an example right there.

I'm personally all for "everything goes", since the adults only settings exist, which might as well double as "disturbing content" filter. At the same time, it's Valve's choice what they want to host, and I don't know a good balance of "reputation vs freedom", which they realistically have to keep.