Have you ever wondered what the "bad vibes" thing is about, when people judge someone else to be untrustworthy?

Well, have you noticed how very often when someone gets called out for some obviously asshole behaviour, shortly afterwards a dozen people step up to say "yeah they've been suspicious for a long time"?

And everybody has their own stories, and individually they don't seem like a big deal, but together they paint a clear picture of someone who knowingly violates boundaries on a regular basis.

Well, that's what the "bad vibes" thing is about. It's people who have experience in spotting this sort of stuff, going "this is kinda sus, and every time I've seen this behaviour before, there turned out to be a bigger problem behind it. I don't have the full picture yet but I'm fairly sure that it's not a good one".

It's a very effective way to deal with the more subtle abusers; and it has a much higher accuracy in practice than you might expect.