I know that I zone out during lectures very readily. I have always been that way. So I amuse myself by half-listening and half-writing poetry.
It lends a pleasant rhyming haze
Over successive lecture days.
People continue to ask questions that aren't questions at all. They consist of rambling opinions punctuated by a perfunctory "how would you respond to that?"
As for responding, my suggestion
Is asking "What exactly was the question?"
That does no good, but it might be satisfying. Perhaps it would be better to respond "Very Interesting!" and leave it at that.