We've been asking for that for a long time, at least for the staff to be able to send a note along with the rejection.
Personally, if I reject an edit and I feel that the choices we have to pick for the reason are not enough to explain, then I will send a PM. But obviously I can't PM everyone for every rejection.
PMing me is not required for wanting to talk about an edit rejection. Primarily because I'm not the only person who goes through the queue. Instead, post into the Listing Errors thread about it and we can take a look. And users may be able to answer the question for you without an admin having to respond.