The official eBay guidance follows. It is not quite as Shangri-La.
Originally Posted by CatLABS
Do I have to accept returns?
No, but you do have to specify a return policy. You may specify that you do not accept returns by setting your policy to “No returns accepted.” If you accept returns, you’re required to accept returns for any reason, including when buyers change their minds.
We encourage you to accept returns to attract more buyers and increase the likelihood of selling your items. All sellers should familiarize themselves with the terms of the eBay Buyer Protection Policy, which offers buyers certain protections if an item is not as described or not received.