

The username associated with every vote, up or down, is available through the ActivityPub API. If your instance doesn’t show them (and I believe lemmy instances don’t by default) some helpful soul has built a tool to view them. Sometimes it fails for reasons unknown, but it lets you see who’s up or down voted a particular post or comment. I believe nom-lemmy interfaces like kbin also show you that information.
We would be overrun by frogs…