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 crypto example was only a suggestion because they have simply solved the exact same problem we are looking at: duplicate votes (transactions) and verifying the results while being able to hide it.
I would love to hear any other suggestions that people may have that solve these problems. Copying open source code from crypto isn’t the only option. So let’s look for solutions instead of dismissals (unless you’re arguing for keeping votes public of course).