This is hard to suggest anything, this looks more like another one of those "online shopping complaints". I just remember from the top of my head that if you deal with a scummy buyer that doesn't pay or pays and leaves negative feedback shortly after, then you can cancel the transaction for any reason and send refund and you will always have any feedback removed because no transaction = no feedback, you just need to report it. The only thing I remember is that if you cancel the transaction for a reason "item is out of stock" then you may get a penalty for it or something like that because you are supposed to have the items you sell or end them on your own beforehand
Personally another good practice I can recommend is turning off any offers and make another claim in the description "I don't accept any offers". This is simply because I kept receiving low-balling spam offers below 10% value with some stupid excuses. Additionally I can remember that many times whenever I accepted an offer and did the transactions, the buyers were usually problematic and were requesting returns and, of course, wanted to make me eat the return shipping costs. Guess if they can't afford full price then they can't afford return prices either, right?? Turn that option off and you can have problems reduced