It's a middle ground between completely hiding the duplicates, and letting them as is. Once you click that plus button, it shows the duplicates as full posts, otherwise it leaves them as just one-liners.
There is discussion on going at !news@lemmy.world currently about new rules. Users posting the same story from the same source will be blocked by an automod. I asked about users posting the same story from different sources, and apparently that's absolutely fine. So expect this problem to get a lot worse before steps have to be taken to make it better :/
The issue is that this sort of rule only works against duplicates inside a community; it does nothing against duplicates across communities, that users may or may not be subscribed to. As such I think that the solution should be on the interface level.
On another, related matter: you replied twice. I think that the server itself should prevent it, as 99% of the time it's by accident.
There is discussion on going at !news@lemmy.world currently about new rules. Users posting the same story from the same source will be blocked by an automod. I asked about users posting the same story from different sources, and apparently that's absolutely fine. So expect this problem to get a lot worse before steps have to be taken to make it better :/