Sellers are not allowed to leave negative or neutral FB to buyers, or leave a negative comment in "positive" feedback.
This rule has been in effect since the middle of 2008, and leaving negative FB with a green doughnut is a reportable offense.
http://pages.ebay.com/help/policies/inappropriate-feedback-comments.html
Sellers can, however, issue nonpayment strikes, which are MUCH more effective than is feedback!
Although we cannot see the number of Unpaid Item complaints filed against buyers, intelligent sellers can block buyers who have more than one UPI strikes in a whole year!
The problems are:
1. Too many sellers do not know how to issue a strike.
2. Too many sellers do not know how to block bidders with strikes.
Are you in either of those categories? If so, let us know, and somebody will give you links to the appropriate pages.
A great place for quick answers; no waiting, no voting,
"Do It Yourself": eBay Customer Support .