On my old Deviant Art, I had a lady tell me she couldn't believe I'd gone to college and my art was mediocre at best. It hurt at first, but later I didn't mind, because it was true. I thanked her and asked for some suggestions on how to improve, and she actually became a friend/watcher. She eventually left DA, and I later closed that account for other reasons.
She was really rude about it, but I was lucky enough to get her to talk and help me improve as an artist. Some people are trolls, others just have no social skills XD