Selective Answering <--- Advice wanted about a person/people who selective answer some part of your email (even after 3..4..5. emails) and not the other stuff.

So you are not getting almost anything back but comms fine in other topics.
A certain very famous Free Soft person I'm communicating with and it's going well BUT any advice?
I almost find it unacceptable, should I just call the person out and see if they have the metal to stand the obvious and even ask to account for it?