If I say "oh, she's pretty, FOR a 16 year old", granted I'm 26. Why is that wrong?
Most Helpful Girl
There's an implication that the compliment only applies because she's coming from a group of people you consider inferior in some way, and it's a qualifier. If you say someone is pretty FOR their age, it's like saying, "Compared to your ugly peers, you're pretty. But you're not pretty on your own, just FOR someone your age."
I think it's more understandable when directed at someone who's underage, to be fair. But it's still language used for an insult, so don't be surprised if someone takes it that way.0