This happened with few people whom I know too. The way these sellers "DEMAND" positive feedback is too much, these days. Even the first time seller is actually kind of threatening the buyers to leave positive feedback only.
They quote "Leaving a negative feedback will not help solve the problem". My point is, if they're really, really genuine sellers, as they claim, why would the problem arise in the first place?
My appeal to the eBay authority is -- negative feedback SHOULD stay in the profile, as that's reality. Sellers, please learn to accept it. Work with eBay to arrive at a dispute resolution policy, in case of a negative feedback.
You people may cheat once, twice or ten times, not always!!