No, sellers can not leave buyers -ve feedback and it has been that way for many years now. If you leave a +ve with a comment that has negative conotation then the 'buyer' can have it removed becasue it is a comment not consistent with the +ve rating (a false positive).  Additionally, you will receive a policy violation from eBay.

What dispute did you lodge with eBay?  If you haven't lodged a dispute the do the UnOaid Item case.  If it was an UnPaid Item case and the 'buyer' does not pay and you close the case they will not be able to leave feedback.  If they leave feedback before the case closes just wait until it closes and ask eBay to remove it.  Don't respond to any feedback they leave.  As much as leaving a false +ve may make you feel better, it is not worth it.

If you sent a mutual cancellation request to enable a refund of final-value-fees then the 'buyer' will still be able to leave feedback for you, but it may be negative and you will have a hard time getting it removed.

Come back here if you have many more questions or need any more advice.