Hermione’s cheeks were going even redder. “You’re really evil, did anyone ever tell you that?”
“Miss Granger,” Professor Quirrell said gravely, “it can be dangerous to give people compliments like that when they have not been truly earned. The recipient might feel bashful and undeserving and want to do something worthy of your praise.
Michelle_Z comments on Harry Potter and the Methods of Rationality discussion thread, part 19, chapter 88-89