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.
Could replace the usernames with UUIDs, and keep the username-UUID map back on the source instance? Then you get an audit trail, but not associated with user identity. There's also no guarantee that people don't use bob_jones as their username, and this is Personally Identifiable Information, which brings up some GDPR stuff too.
