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.
Your idea assumes that you can just change the protocol. The ActivityPub protocol is developed under the W3C. If you just change something you are no longer compatible with other services.
I didn’t intend to imply that only one server changes something. I was intending to imply that the protocol should be updated (after review, ratification, etc.). I’m sure there’s edge cases I haven’t considered.
This part of the protocol is not explicitly defined. In fact, section 3.1 of the AP spec says that null may be used to signify an anonymous identifier, then additionally these activities could be tagged using extensions to contain a unique identifier that isn’t the actor. The more you look at AP, the more you see how loosely it’s defined, and for good reason, it allows it to be applicable to many different scenarios (a twitter, a FB, and now a Reddit). What he’s suggesting would make it not interoperable with things like Mastodon which require an actor for a Like, but it’s not changing anything about the protocol.
EDIT: By the way, other things don’t work when viewing Lemmy comments on Mastodon too, like downvotes don’t do anything on the Mastodon end. And you can follow Lemmy users from Mastodon but not the other way around.