See-through skirt??

I am a postdoc in her early 30s. I am Italian and this happened at a conference in Italy.
After my talk, an academic in his 60s, who had previously asked me a (not particularly smart) question, approached me and said: “You don’t see often women giving talks in see-through skirts, I am impressed”.
Needless to say, my skirt wasn’t see-through, it wasn’t a mini-skirt, and I was wearing thick black tights.

I replied politely, pointing out that my skirt wasn’t see-through.