In my many-year experience on eBay, it is rare that someone wants a refund for any reason. I have no doubt whatsoever that the buyer realized that he paid way too much (in my opinion) for that freewheel. His saying "I don't like the sound" is BS and that makes him a putz.
Honestly, I really appreciate retail stores offering very generous return policies- I have taken advantage of them many times. And, even though eBay auctions aren't equal to retail stores, I always conduct my sales with the attitude that if both parties aren't happy, then it was a bad deal.
I'd accept the return- some deals work out fine, and some don't, that's the way the cookie crumbles for me.
I would clearly warn him, though, that if there is ANY damage to the removal notches, the deal is OFF. He has to take the good with the bad too.
Minneapolis MN USA