The best part of the fediverse is that anyone can run their own server. The downside of this is that anyone can easily create hordes of fake accounts, as I will now demonstrate.
Fighting fake accounts is hard and most implementations do not currently have an effective way of filtering out fake accounts. I’m sure that the developers will step in if this becomes a bigger problem. Until then, remember that votes are just a number.
The nice things about the Federated universe is that, yes, you can bulk create user accounts on your own instance - and that server can then be defederated by other servers when it becomes obvious that it’s going to create problems.
It’s not a perfect fix and as this post demonstrated, is only really effective after a problem has been identified. At least in terms of vote manipulation from across servers, it could act if it, say, detects that 99% of new upvotes are coming from a server created yesterday with 1 post, it could at least flag it for a human to review.
It actually seems like an interesting problem to solve. Instance runners have the sql database with all the voting record, finding manipulative instances seems a bit like a machine learning problem to me