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 difference is that this data can already be surfaced by anyone, all they need to do is spin up a federated instance, so someone could do all the stuff outlined in the parent comment, but keep the results for themselves, or monetise it, build advertising profiles, doxx people, etc.
The data already exists, and it can already be extracted and made public (or used privately). I’m not saying throw open every database to the world, I am saying the world can already access this database, so pretending that it’s not available doesn’t stop bad actors from using it. Might as well make a public tool (that actually sounds kinda cool?) and bring awareness to it.