[thstone]

Keithl's approach is very sound...

However, I will take a slightly different approach and assume that the seller won't send you the refund until you post positive feedback first.

If your goal is to get a refund and you don't care about the feedback, then leave the positive feedback and hope that your postive action will motivate him in a sense of reciprocity to do the right thing and send you the refund (since you did the right thing first). In terms of karma, postive energy creates more positive energy. Its a beautiful thing.

And even if he still stiffs you on the $80, you'll know that the positive karma is on your side and that one day he will get his due.

If your goal is to burn him on the feedback, then leave negative feedback now and write off the $80. In terms of karma, uh, not so positive.