Working with mme_publisher, we've seen some strange responses to rejections. (nihilistic_kid talks about that a lot with Clarkesworld as well.) When a writer posted to a chat board that Polyphony had rejected his story because it was too ployglot and European in its sensibility, and we obviously didn't understand it, she and I knew about that right away. It was obviously ridiculous defensiveness, and we had a good laugh over it, but if the writer had been a bit nastier about it, their name would have been noted. I had another writer go ballistic on a mailing list when my rejection to them suggested they might not want to use the editor's name as a character name, simply because it's very distracting to read and subtracts from the editor's chances to be submerged in the story. Again, I found out about it in fairly short order.
It's a small Internet, people, and very well indexed. People know when you bust out the insecurity. If you're nasty enough, people remember it. Every editor has a kill file, usually reserved for the sorts who write threatening cover letters (and yes, that really happens). Right now mine is one name long, the gentleman who made a threatening comment on this LJ last year. And believe me, you don't want your name featured in a kill file story told in a bar at a Con.
My recent high school metaphor received a very mixed reception. Here's another place it applies. Not tribalism or cliquishness, but the fact that just about everybody working professionally in the field knows each other, or are at most one degree of separation apart. If your temper gets the better of you on receiving a rejection or reading a bad review, for the love of Piet, don't blather about it on the Internet. At best you'll look like an idiot. It goes downhill from there.