Kbin does that in terms of function as in kbin has its own microblogging element to the experience, but it doesn't do anything to bring the existing kbin and mastodon universes together.
Mastodon can do this. Mastodon interprets Lemmy communities as users, Lemmy threads as boosted posts with user mentions, and Lemmy comments as replies. If you search on Mastodon for a Lemmy community using the Mastodon format e.g. @community@domain instead of !community@domain you'll find the community and posts.
I just wish browsing communities on Mastodon was cleaner. Instead of seeing posts to the community, you see every comment posted instead. If that aspect changed, Mastodon would be almost perfect.
Agreed. There's an option in Mastodon to hide replies in a feed which in theory could solve the problem, but it never hid anything for me. Maybe try that?
I've tried kBin and it's basically Lemmy and Mastodon merged together into a single app. You can follow communities and people.
IMO it just doesn't feel right though. It feels like it's trying to be both while failing to be good at either. It's a subpar Lemmy experience and a subpar Mastodon experience.
If browsing communities on Mastodon wasn't such a nightmare I'd say just do everything from that app.
You should still try kbin though to see if you like it.