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.
The problem is that it’s actively worse than Reddit. While only Reddit employees can access your data and it’s being sold to the highest bidder, Lemmy sells your data for $0.00.
Anyone can become an instance admin through their own instance, so your voting data is pretty much unprotected. That is the opposite of privacy. I get that it’s a consequence of the fediverse, but then it just may not be the solution to social media.