I was reading this question about famous people asking rude questions in talks, and it reminded me of a situation which happened at the end of my academic career. I would really like some advice on how I should have handled it.
I was giving a short talk at a conference and at the end the session chair asked for questions or comments. An eminent Belgian professor said "I really think you should look at X from 197y" and, since I had looked at X, I began to reply, and then the professor interrupted my reply with
"That wasn't a question. That was a comment."
I was speechless. This is Treppenwitz as it was several years ago, but what would have been a good comeback?