I would still prefer to sell/buy used privately. There is very much a gray area buying used audio gear online and I prefer the matters being dealt with directly between buyer/seller. As a buyer/seller of used gear they are assuming all the risk and to have the funds tied up with a middleman complicates matters especially if problems arise with the product and refunds. For example an individual buys a used receiver and it breaks down in 14 days. That is past the return period but as a seller I would still refund them but can't because that money is tied up in credit. As a credible seller I still refund them the money and take a big hit. Getting cash on a sale is always better than store credit and any small unused credit after upgrading is pretty much useless like $20 or possibly even $100. I would rather have that $20 or $100 in my pocket.
The only advantage I see over selling privately in a classifieds section on a audio forum with Paypal is transaction security and bringing a level of legitimacy to the seller.
I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.