My understanding is that this "replicate a community with old posts on another instance" is some feature that was added to PieFed that I assume that @[email protected] used.

https://piefed.social/post/667045

EDIT: Oh, awesome! It looks like this feature also replicates the pict-rs-hosted images.

So, for example, take this post:

https://lemmy.today/post/30543446

It has an image. The submitting user uploaded it to lemmy.ml's pict-rs instance (which is what happens on your home instance when you use the "upload image" button).

That was potentially a problem for users on lemm.ee, because when they upload images, they upload the images to the lemm.ee pict-rs instance, and when lemm.ee goes down, the images will stop being available.

However, as you can see, here's the PieFed version of the post:

https://piefed.social/post/805357

And the image there is hosted on media.piefed.social. That is, this PieFed community migration feature will apparently preserve a copy of anything that lemm.ee users have posted to this community.

Still going to be a problem if lemm.ee users have posted images to other communities (say, for example, [email protected]), since when lemm.ee goes down, those images will become inaccessible, but at least it means that this community will retain content.

Does mean that PieFed's community migration might consume a lot of disk space on the PieFed instance, though...