I don't really get it. The image is federated, there's no need for instances to refetch it. Just checked out some posts and indeed it's there, in the image property. With the URL pointing to the Lemmy instance. So if this is actually an issue, that's just bad programming and needs to be fixed. Edit: didn't notice OP uses Piefed. Unlike Lemmy and Mbin, it seems like Piefed doesn't federate it. Edit: actually I'm blind, Piefed does federate it too, sorry piefed