YSK: Your Lemmy activities (e.g. downvotes) are far from private
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.
Redditors already scream at people when they get a downvote and blame it on the person that replies to them, even if that person didn't downvote them.
I can see this being dangerous and leading to a lot of bullying. I know k-bin already publicly shows this. I can see who downvotes my comments/posts when I open up the post in a k-bin instance, without even being a member.