Not that I’m aware of. The Lemmy APIs provide access to that data but I don’t know of any existing tool that uses it for the purpose of exporting posts or comments.

All your old stuff will stay visible even after lemm.ee goes down, but it won’t be linked with whatever new user you create on another instance.

If export and import of posts and comments was possible it would result in “duplicating” your posts and comments to your new account, which as you might imagine would be an absolute mess (not to mention technically infeasible - how would comment chains with other users work?) so you can presumably understand why it isn’t.

It’s quite annoying for sure (and I’m a lemm.ee user too, so I’m also annoyed with everything I’m losing) but this is the trade-off we accept with federation that allows Lemmy as a whole to be robust and keep going even without lemm.ee

And you can say no if you want to!

Its not, but you can’t just keep a passenger on your plane who is flipping out and might try something else crazy apart from that.