Oh yes, right, that is how it works with subscribing to a community.
Though, if I’m on my instance, and select a community from another instance to post in, the post ends up on that community and I have a copy of it (it seems, that’s what I did in this case).
Another comment mentions that if the community went away, I’d still have a copy of the content, which is interesting, though not entirely useful for picking up where the original community left off?