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.
On encrypting messages, this is a solved e2e problem if users home instances generate public private key pairs for its users on sign-up ( or users can provide their own )
Then the instance admin holds the private key and can still decrypt.
If you cared that much about privacy in DMs, we should have a “profile page”. Post a PGP public key there. Then you can send PGP encrypted messages to anyone who you have a public key for.