As far as I'm aware, Delcampe is the only platform that allows a buyer to block a seller, and I've got a long blacklist! Sellers who find it impossible to present a clear image are top of my pile.
If you hover over an image, a heart and three dots appear. Click on the dots and a drop-down menu appears giving you a range of options, the last of which is "Hide the Seller's Items". Click on that and another drop-down appears. If you select "Not Specified", the seller isn't informed that they've been blacklisted. Select any other option, and they will be informed, but they won't be told who blacklisted them.
A very handy tool to filter the rubbish out of your feed