I usually don't look at the top of peoples heads in so much scrutiny and I don't if other people do so either. The thing that triggered it off for me was an article I read online in which the quote said "ideally your head should be symmetrical" this article was about head shaving. I've had my head shaved now for about 3 weeks and nobody has made a comment like that except my mother who obviously remembers me as a baby. Obviously the person who would look at me in detail would be my wife and she hadn't noticed till I told her, when I did she just said it was very little and under "normal" circumstances it won't be detected unless you asked someone to look for it!