ebay is totally prejudiced in favor of buyers and against sellers.
the age-old "supply / demand" equation: if a demand exists, somebody will jump up to fill it.
reading the fine print tells a seller that if he has delivery confirmation, he is safe. when I started on ebay, I did not use delivery confirmation until after I had been screwed by an international buyer.
well, "screwed" is a relative and/or philosophical concept: am I, the seller, unconditionally guaranteeing that the item will arrive safely in his sweaty hands, or am I guaranteeing that a well-packaged item will be posted promptly?
this buyer said he never got it, and he lived in Ireland where the US Post Office could not confirm delivery, so Paypal sucked the money out of my account immediately, without even notifying me that there was a complaint.
eventually, I put a statement like "not responsible for items shipped internationally" in my terms and conditions statement, and have not had a problem since.
whenever I did have a problem, I gave a prompt full refund, or shipped a new item, if I could, immediately.
that has kept me safe from negative feedback, but I have still had a few flame battles with hostile weirdos.