"It was a pity you lost your leg and had to do this compulsory marathon on crutches, I bet you could have ran it faster if you had 2 legs!” I mean, she knew she only had 1 leg right, so it's valid feedback. So yeah, definite dick move. Better to focus on feedback they can control (stand up straight, content of their presentation, etc) rather than call out the one thing that's hindered them likely all their life.