I recently had a non paying bidder. I filed an unpaid item dispute, they never responded so I filed for a Final Value Fee credit and they received a strike. I felt safe enough to leave appropriate feedback as they had not responded. eBay allows the seller to feedback but not the buyer if they fail to respond to the dispute.
I relisted the item, which subsequently sold. The day it sold the non payer...out of the blue suddenly paid. I immediately refunded their payment with an explanatory note.
I recently viewed my old disputes only to find that this member had obviously appealed their strike as they had 'proven' to eBay that a payment was sent. I was not informed of this, I lost my final value fee credit and the strike is now lifted. My concern is also now they may be able to leave retaliatory feedback.
If you received an unwanted payment from an NPB which you had to refund...double check that they haven't appealed their strike....sellers will lose out.
I await a response from eBay and will update once I hear something.