Buyers have not been able to receive anything but positive feedback since 2012.
Even back then when buyers could receive negatives, buyer feedback was not a useful metric for evaluating buyers, for the simple reason that in most cases, by the time a seller is in a position to check the feedback of a buyer the purchase is already committed to, and because eBay never permitted sellers to cancel a transaction due to "bad buyer feedback".
Allowing buyers to get negative feedback lead to sellers using the threat of negatives to discourage buyers from giving sellers well-deserved negative feedback. Some sellers would give retaliatory negatives and use mutual withdrawal to get their own negatives removed, driving away good buyers from the site and making it harder to distinguish between good and bad sellers (which is the whole point of the feedback system).
If a buyer does not pay, the proper course of action is to cancel for nonpayment after four days. That is the only thing that helps other sellers by ensuring that the account receives an unpaid item strike which can allow other sellers to pre-emptively block that account from bidding or buying through to the sellers' buyer requirements.
