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.
You can do it on your own instance, but the way Lemmy works means you’ll need to do some changes to both native code and SQL queries to make it work reliably. Every instance has complete control over how they display other instances’ data.