Ebay conditions state
"We only remove feedback comments if they break the rules of our feedback policy. Please review our feedback policy to see if your feedback qualifies for removal.
In most cases, feedback left for you by another eBay member cannot be removed. A belief that a comment is untrue, undeserved or left in retaliation is not one of the circumstances in which we'll remove feedback."
I think under these circumstances I would forget about the feedback.If you keep e-mailing the seller he or she might just leave you a negative.