here

I don't think they do mutrual withdraw any more, do they?

http://pages.ebay.com/help/feedback/remove-withdraw.html

and
http://reviews.ebay.com/THE-TRUTH-ABOUT-REMOVAL-WITHDRAWL-OF-NEGATIVE-FEEDBACK_W0QQugidZ10000000002574231

or the easy way:
wait 12 month , it will expire.