A recent teacher: "What are you doing with your arm...is that intentional? Did you get that from Youtube?"
[no it wasn't intentional, but I think I had been watching a Taubman video!]
Not sure if this counts, but I remember a recital coordinator who, right after every student's performance, always promptly said something nice about the performance like, "Beautifully played", "I loved your energy" "I love how you kept that tempo". It was all children and I was the only adult student, and when my turn came, I bombed. He paused for several seconds and then all he could manage was, "Um...that's a really interesting piece...I have to remember that version." I can chuckle about it now though!