You are changing the question to "is a perfect replica of a person considered the same person or not?". That is not the question.
What you experience by using a teleporter is you enter a room, and then you die. End of story. There being another replica of you somewhere does not change that you died. For an outsider they may argue whether or not you died, whether or not the replica is you, and so on. But from the perspective of someone who enters the teleportation room, it's over. Dead.
The problem is that while subscribed you see the popular posts twice. All of them. Sometimes even literally one after the other in the feed lol
Right now we just choose between seeing almost everything twice (sub to both) or missing a little (sub to only one).
From a different end-user POV, seeing the same stuff repeated is not fun. I would prefer to see everything once instead of choosing between seeing almost everything twice(subscribed to both) or missing a little bit(subscribed to one, blocked the other).
It used to be that way on Reddit before they changed the algorithm to force old posts (older than 12 hours and then 24 hours and so on) to fuck off from the front page. It's also a problem that multiple instances show you the same post repeatedly, so a popular post on the front page stays there for a whole week and you will still see it even if you scroll past it.
Lemmy devs simply do not address the issues of the platform.