At most busy dropzones and boogies, anyone with an A license can easily manifest on a load and then walk out to the loading area with the newest biggest ws without any question. We don't have gear police checking licenses and jump numbers before someone boards the plane. As a used gear seller, you may be the last person in position to prevent an idiot from becoming a fatality at a dz or going in at someone's local E while reenacting Jeb's latest youtube stunt. While I'm a big believer in Darwinism, DZ fatalities affect not just the deceased and their immediate family, but all the fun jumpers, staff, and the flow of potential tandem customers. Used gear sellers bear a moral responsibility to the skydiving community, not just the person they are selling the gear to. Personally, I'd like to see manufacturers register advanced gear (canopies, ws, base gear) to a buyer. If you sell a Vampire to a total wuffo/ newbee who goes in at my home dz, your ass should be held somewhat liable.
