I am not an expert on this, but I think the kind of person I have in mind would not bother to look for willing BDSM victims. From their point of view, there are humans all around, and their consent is absolutely irrelevant, so they would optimize for some other criteria instead.

Human beings frequently like to think of people they don't like and understand as evil. There various very bad mental habits associated with it.

Academic psychology is a thing. It actually describes how certain people act. It describes how psychopaths acts. They aren't just evil. Their emotional processes is screwed in systematic ways.

My best guess at this moment would be to create a community where people are more open to each other, so when some person harms another person, they are easily detected, especially if they have a pattern.

Translated into every day language that's: "Rationalists should gossip more about each other." Whether we should follow that maxime is a quite complex topic on it's own and if you think that's important write an article about it and actually address the reasons why people don't like to gossip.

I think someone should at least try to solve this problem, instead of pretending it doesn't exist or couldn't happen to us.

You are not really addressing what I said. It's very likely that we have people in this community who fulfill the criteria of clinical psychopathy and I also remember an account of a person who said they trusted another person from a LW meetup who was a self declared egoist too much and ended up with a bad interaction because they didn't take the openness the person who said that they only care about themselves at face value.

Given your moderator position, do you think that you want to do something to garden but lack power at the moment? Especially dealing with the obvious case? If so, that's a real concern. Probably worth addressing more directly.