How would this work in practice? I upvote a post and it sends the upvote via a token user to another instance. Then I remove my upvote or downvote instead. My instance would then need to send an undo or dislike for the token user too. How would you ensure you have enough token users to fill up all the votes on a single post? You'd need thousands if not tens of thousands of these token users. How does it work when I ban one of these users? How do I prevent a user from participating if they use these token users?

Also, this could be used to make vote manipulation easier I bet.

[–] Socsa@sh.itjust.works 2 points 3 months ago

The simplest form of this is literally just a token which replaces the universal identity. So you ban the token, you ban the user. This only applies for voting anyway, since commenting and posting follows the plaintext user agent.

A more robust trust model with rotating tokens would fully move ban enforcement to the home instance, which I actually believe is already the case in some situations. Eg, when I am banned from a specific community on another instance it seems as if my host instance knows not to even display a vote on the UI, which suggests that it has knowledge of my federated ban. With this trust model it would be possible to fully enforce cryptographically secure forward security as well.