I figured the lack or response meant no one has any idea what measures to take, though there are probably a number of sellers who have unknowingly experienced this (eg the affected seller may only get the genuine buyer's details [more so if it is a website purchase], so they contact them and say "why have you initiated a chargeback?" and they only get the "I haven't", or some variation thereof). 

The scammer is still operating, sadly, though they removed the items listed that came from the seller I'm in contact with (partly copyright issue, partly knowing they were never going to be able to successfully complete a purchase of those items again). The other affected sellers were contacted, but they weren't overly concerned for some reason - their items are still being listed / sold, but maybe no chargebacks yet. 😕