I've sold lots of stuff on Ebay. And I think I have left negative feedback for about 10 buyers: they were all people who bid on my listings and then didn't pay.
This new change just sounds incredibly stupid. If anything, buyers who have feedback left for nonpayment should be blocked from leaving any feedback for the seller in the transaction. The new change makes it incredibly easy for dishonest buyers to defraud sellers: just claim the item never arrived, even if it did, and then leave negative feedback for the seller. Then file a Paypal dispute and get a refund. And then there's absolutely nothing the seller can do about it except complain.
After enough similar complaints, Ebay and Paypal will eventually close the problem buyer's account. But this will happen only after a lot of honest sellers have been ripped off.
Doesn't look like I'm going to be selling anything else on Ebay.