Thanks for digging that up. Had been one of my outstanding questions. I agree with the initial requestor of that issue; it will be a major source of friction for users migrating to Lemmy from Reddit.

I'd like to be able to at least manually trigger the retrieval of a set of posts/comments as a user. Otherwise as the requestor noted, its going to make interacting with "new" communities difficult and unintuitive if you can't see comments from before when it was synced to your local instance.