so while a bit young, you'd think old enough to handle criticism

I dunno. Fourteen-year-olds often have a lot of growing up to do. His/her response to you was still pretty darn immature, but...I dunno, I think a lot of people that age get defensive and wanky. Not everyone is like our wonderful younger Quillers.

But I still agree that the author probably wasn't looking for criticism, but rather praise and a self-esteem boost.