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.
Unfortunately they could just spin up a lemmy instance on some anonymous server somewhere and do that anyway. I don’t want them in here, but they can certainly already pull the data up. To me that necessitates some form of anonymizing protocol, or even a form of shared encryption making it so you can’t simply pull data in, you need to be invited or allowed into the federation.