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.
Is the poster’s IP address, system, or other system identifier/location, tracked?
If I have users giantshortfacedbear and throwaway123. Then it could be inferred or impled that they are same person if there are from the same IP or phone.
That information is not tracked in the application itself. A “home instance” admin could correlate their web access logs with the database to draw this kind of conclusion but it’s not federated info.
That’s good at least. This means that I only need to trust the host for my home instance keep my anonymity.
I believe that information isn’t sent over ActivityPub protocol so while the instance admins individually could see it, it isn’t federated data.
Though if account association by IP address is a concern for you then you should probably be using Tor to connect with your accounts.