It would be nice to block a user that never shows up, or you know that has no intention of buying. Window shopping. Just wasting your time and effort to sell on site.
I don't think that reporting them is appropiate for this. As they have not done any illegal per say, just annoying for sure and not going anywhere with their offer.
Totally hear you on this feedback, @jvoffers! Being able to block without first submitting a report against the other user has been requested before. If you block a user, this will block any communication.