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.
There is a person working on a blockchain version of Lemmy for the purpose of making the data content addressable and allowing it to be shared in a peer to peer system so that the main instance server gets less load. It seems like GDPR is getting in the way of progress or that devs need to do a lot more work on trust in the swarm to make it work.