Instances are more like servers or domains. Your instance is lemmy.world. We can see votes from individual users because votes federate across instances, (like if you, on lemmy.world, were to vote on my instance, lemmy.dbzer0).

In order for that federation to happen, the votes must be public. This prevents a rogue instance from just lying and telling other instances “yeah all my shit is super upvoted” and pushing itself to the top, or inversely pushing others down by spoofing downvotes. It also allows instances to properly block banned users; If I’m banned from a community/instance, my individual votes shouldn’t count towards it. So anyone with the know-how can inspect which individual users have voted on posts, and how they have voted.

Someone spun up three entire instances and mass created dozens of accounts on each, just to mass downvote. It’s just blatant vote manipulation, and is why the admin stepped in to defederate (stop sending info back and forth) from the rogue instances.

You see stuff like that occasionally from the “tankie triad” instances, (lemmy.ml, hexbear.net, and lemmygrad) but they’re usually more subtle about it to avoid instantly getting defederated.

Little bit more.

Someone made 3 servers, then a bunch of accounts on those servers, then used all of those accounts to downvote.

Allegedly because I ain't got the time to manually verify that myself.

Servers, not users. Though each server would have users.

Although I don't think they're bots like the post is implying. OP just spends a lot of time annoying them.

What do people said, but since you're new, here's a recap post on what the whole Tankie situation is about (if you didn't encounter them on Reddit lol