When you vet someone for whether you can be close friends with them, what's a seemingly unimpactful characteristic about someone that would instantly rule them out as a potential close friend for you?

I read somewhere that apparently lefties aren't as susceptible to knowing which toilet paper direction is objectively correct.

So it's basically like one of those mini-disabilities, like being horrible with directions, or not being able to remember peoples' names. Go easy on the poor fellows, they can't help it.