As a response, I’m trying this out: PieFed accounts now have two profiles within them - one used for posting content and another (with no name, profile photo or bio, etc) for voting. PieFed federates content using the main profile most of the time but when sending votes to Mbin and Lemmy it uses the anonymous profile. The anonymous profile cannot be associated with its controlling account by anyone other than your PieFed instance admin(s). There is one and only one anonymous profile per account so it will still be possible to analyze voting patterns for abuse or manipulation.
ActivityPub geeks: the anonymous profile is a separate Actor with a different url. The Activity for the vote has its “actor” field set to the anonymous Actor url instead of the main Actor. PieFed provides all the usual url endpoints, WebFinger, etc for both actors but only provides user-provided PII for the main one.
This will be a bit controversial, for some. I’ll be listening to your feedback and here to answer any questions. Remember this is just an experiment which could be removed if it turns out to make things worse rather than better. I've done my best to think through the implications and side-effects but there could be things I missed. Let's see how it goes.
Is it possible for an instance to send out false vote data that can't be verified? Lemmy doesn't seem like a plausible target for it at the moment (and i dont pretend to know how this works beyond a conceptual level) but I can imagine a bad actor at some point seeking to manipulate voting.
I guess that can happen now anyway as the bad actor can just create their own instance with as many fake accounts as they like. Ultimately it's still on other instance admins to block the dodgy ones either way.