I know what you mean - I had a sorta Draco (not anywhere near as bad) and I found out quite by accident that she was a cutter, too. She never knew that I knew, I don't think, but it certainly changed the way I saw her behavior. I switched schools soon after that (unrelated issue), and out of all the people from that school, she's the one that I remember most clearly. She was horrible to me and then I saw that she was like me in a very fundamental way. So I remember her more deeply than the people that I was friends with, even.

People who cause pain tend to be in pain, I've found.