Tom wrote:
"He returned my bid plus shipping (and offered return shipping, too)."
Positive feedback. Absolutely. You don't have to say much -- you could say "good guy", or "seller has integrity".
The guy did the right thing. He should get positive feedback, just like you'd feel good about a store that screwed up a sale, but totally took care of you when they learned about it. You can try to psychoanalyze him, and figure out whether he did it intentionally... but you'll just be guessing, and besides, he offered to eat the shipping.
$.02 worth
Peter Bridge
Denver CO