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 wouldn’t say Lemmy doesn’t care about your privacy, but probably they didn’t have enough traffic before the death of Reddit to really prioritize it. I myself have security concerns, particularly with the storage of account data on servers that who knows where they are hosted or what the security is. But I would say Lemmy instances are much more likely to be targetted for attacks by malicious hackers than Reddit, because most instances are likely hosted on far less secure machines than Reddit servers.
Not that I don’t agree but there is a pretty big citation needed there.
We don’t really know how secure Reddit Servers are and their attack surface is likely to be far larger.