IIRC you get to see who left reps if you are a paid member. I agree with you about only giving neg reps for insults and stuff like that. Every one of the negs that I've got make no sense. Bugs me a little but then I remember that rep doesn't actually mean anything so I just don't worry about it.
Jon Jones, Demetrious Johnson, Renan Barao, Marius Zaromskis, Douglas Lima