Lemme explain with subreddits.
You have /r/tech and /r/technology, right? Different subreddits, different communities. Somebody posts something on /r/tech and crossposts it to /r/technology. You’re subscribed to both. You now see the same link twice.
That’s exactly what’s happening here, cross-posting to different communities. It’s still the wild west out here, but I would expect a lot of these communities to solidify behind 2-3 “winners” over time, with the smaller ones becoming more niche.
Reposts are an annoying part of reddit, but I think on Lemmy, different communities on different instances will have different takes on things and the hivemind won’t form as easily.