Threadiverse people: yes that's a good idea. Also this is already done because of how the threadiverse works.

Microblog people: are you insane that's a violation of my privacy. You're not allowed to scrape my public posts. *blocks*

And that takes lot storage space, should my data remain that long ? If it was a newpaper, a personal blog, a diary, bookmark...i would save them.

Two PieFed instances do communicate the post history upon subscription. And, I think, comments as well? But PieFed cannot do that with Lemmy.

After all, all messages here are copied to many servers, each of them already serves as a backup. One more backup doesn't make much of a difference.

Lemmy.world, sh.itjust.works and lemmy.zip are examples of instances that have existed for a long time and are well federated. Almost anything gets backed up by them, because almost any comm has users from those instances.

See for example the case of lemm.ee. It went down. Yet, here's an example of its content being live and (somewhat) kicking: https://lemmy.world/c/movies@lemm.ee .
Their closure was known before, so communities names were appropriately changed.

How the Forumverse works is that each instance that has at least one user subscribed to a comm makes a full copy of all of the comm's text material whenever something gets published there. What, however, goes missing is the ability to propagate the content between instances. That would be the job of lemm.ee, in this case. If you now go and write a comment at https://piefed.social/c/movies@lemm.ee , it will never be visible when viewed from within other instances. In other words, whatever you comment there, will not be visible on https://lemmy.world/c/movies@lemm.ee, because you are not a user of lemmy.world and nobody's there to federate the content.

I wish Forumverse comms had some kind inheritance tag so that a comm could tell what instance should gain the right/responsibility to do the federation work if the comm's original instance is confirmed to have gone belly-up. If that was done, comm's would be essentially eternal. Now it's a bit of a weird situation that you have comms that look completely existant and where it looks like you can even comment, but the comments won't propagate anywhere.

But the content is still there. If you subscribe to a community, it means all of that community's text content (but not images!) will be backed up on your home instance's server.

There is no point on keeping every stuff we created there. Maybe for history purpose on how we lived here ? On old computer ? On good photo and memory ? Nostalogia ?

Dunno...internet and memory from past is an interesting topic.

Edit: typo