if you don’t have a case, drawing further attention (especially if annoying you is part of their marketing effort) likely helps them attract more buyers, so may be best to just let it go.
Discussion
IMO not everything should be adjudicated by the legal system. Even if you are in right it can be too costly to discover the pseudonymous persons involved. It seems sufficient he raised awareness of the problem so others recognize it when it happens again. Other devs and famous names are similarly being invoked in acts of misrepresentation that borderlines on theft. The community should call out these acts as wrong when they see it.