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.
I’m confused by OP entirely - wasn’t your upvote/downvote history an option to display an reddit and turned on by default? Of course it’s logged in a database an accessible by administrator, how else would it know what I’ve upvoted and downvoted before?
No, if you go to old.reddit.com/prefs/ the “make my votes public” defaulted to keeping votes hidden from other users.
Most users from Reddit that are coming here are voting while not realising that their votes are completely public to anyone that simply uses kbin to browse through any instance.