You're obviously angry, but do calm down before you make any irrevocable decisions.
You're complaining - rightly - about buyers who you feel are gaming the system. This latest one sounds as if they may have opened a case for the wrong item: did they explain why they did it , if they're happy enough to buy again? If so, you could ask them to close it. (eBay staff used to close the case for you, if there was an eBay message saying the customer was satisfied, but I don't think they're allowed to do it nowadays.
It sounds as if you've had a run of bad or careless customers. Honestly, that can happen anywhere. But if you're going to carry on selling (whether on eBay or elsewhere), you will find it easier if you can work out a way to handle customer problems calmly, sympathetically and professionally, rather than assuming the worst or calling your customers scumbags and morons. Personally, I discuss difficult customers with a family member who ALWAYS takes the customer's side. It calms me down, shows me the other point of view, and helps me work out possible solutions that will make the customer feel valued and won't break the bank.
I try to do this before leaving feedback or replying to customer complaints, because each immoderate response is permanent, and will be seen by potential customers.
For your own peace of mind, it's best to approach these problems calmly. If you can try to rise above the rudeness from buyers, the unfairness of eBay rules and the unhelpfulness of some of their CS staff, you may find a way to de-escalate things with your buyer so you can carry on selling without so much stress.
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Cesario, the Count's gentleman
