Going from 5mm to 30mm range doesn’t really overlap with Bluetooth use cases.

By default, instances can connect with any other instance, but admins can block instances. The connection is made when a user on that instance subscribes to a community on a different instance. You can definitely run your own instance and just disable sign-ups.

https://join-lemmy.org/docs/administration/federation_getting_started.html

I think it actually drives people away from reddit, since they aren’t finding the content they’re looking for. Just read this post the other day: https://lemmy.dbzer0.com/post/81954