Buyer didn't know how to pack and return a coin. All you can do is refund them if it had tracking. Insured is more for an entire package to be lost...not for missing item in envelope. Although you know how to pack a coin like other sellers...sending coins in a standard envelope shouldn't be done anymore. There was a time in the past where there was refunding and people would get coins as a refund in the mail but that is long gone. There are newer machines sorting mail that will not take coins mailed in an envelope. Not all post offices have these machines so it's like gambling as to whether the envelope makes it to its address. I don't think it was the buyer's fault at this.
However,
I can understand blocking the buyer on the return since we prefer not to send something on approval. Coins used to be sent on approval in the mail years ago. With great photos a buyer can see what they get. You are right to block them.
