I am new and trying to understand how Lemmy works. I am posting this from my lemmy.world account, on a lemmy.ml community. It seems like you can read, post, subscribe to whatever community outside of the instance you’re registered with. So… Why register on lemmy.world vs lemmy.ml or any other instance, if all communities are accessible to everyone?
Also new to Lemmy, but it looks like it only really matters which instance you register with if the instance shuts down (your account will be lost).
You should also try to pick a smaller instance, to avoid unneccessary load on the few ‘main’ ones, but also make sure you’re on a reliable instance, since you’ll lose access to Lemmy in downtime.
Also, when communicating with other instances, they can see the one you signed up to (I’m on sh.itjust.works).