Edit: obligatory explanation (thanks mods for squaring me away)…
What you see via the UI isn’t “all that exists”. Unlike Reddit, where everything is a black box, there are a lot more eyeballs who can see “under the hood”. Any instance admin, proper or rogue, gets a ton of information that users won’t normally see. The attached example demonstrates that while users will only see upvote/downvote tallies, admins can see who actually performed those actions.
Edit: To clarify, not just YOUR instance admin gets this info. This is ANY instance admin across the Fediverse.
We can monitor actual active users that an instance has. Anything artificial in volumes enough to have an impact would be noticeable in some way to other instances.
Can’t someone talk ActivityPub directly and do this? If the instance is responsible to authenticate the users, the instance can just directly talk ActivityPub to the rest of the network and tell it users and votes on the fly, without even Lemmy running there.
Given the number of lurkers on Reddit, you would probably end up with a lot of false flags.