One thing that I think should be acknowledged in this thread (and to my shame only occurs to me a few days late) is that feedback is an issue that new users naturally are far more concerned about than old-timers. My first few transactions, both on this and on other sites, I was quite uptight about getting my feedback, I wanted it clear to everyone that I had my running shoes on and was doing my best to get round the track.
After a while I mellowed, as no doubt most do eventually. Double figures even! Somehow one missing feedback is no longer a slap in the face. And then a neg arrives from some clueless idiot with all the communication skills of a caterpillar. Suddenly feedback is really important again. But the hurt fades.
Is there a moral? If there is, it's keep trading, stop worrying.