Esteemed Miss Snark:
Some of us have been engaged in spirited discussion re: whether an author is "allowed" to correspond after a NMR (negative market report, i.e., rejection. Some of us have sent a short note thanking an editor for looking at the MS and asking what they liked about it. An editor on this loop said this was rude and she wouldn't answer such a note.
What do you think?
Well, I like the 'esteemed' thing, I may put it on my business cards.
You are "allowed" to correspond with anyone the law allows. Whether it is a good idea is another question. To my way of thinking someone asking for feedback after a rejection is raw meat to the wolves. If they ask, I've been known to send them my unedited reading notes. This is how NASA plans to populate Pluto cause after reading them, people have been known to go into orbit.
Agents and editors are well within the bounds of courtesy to not answer such letters. No guff from me about that at all. From our perspective it's not that we don't want to tell you, it's that it seems to open the door to further questions, clarifications, and worst of all..submissions. I cannot spend time answering questions about why I didn't like something every day or I'd never get to my paying work.