I think this should be added to the pinned post. The current wording is a bit misleading:

Because of how Lemmy is built, everything posted on lemm.ee will still be accessible from other instances, even after we go offline.

I forgot doing this before feddit.de wasn’t reachable anymore which results in my image posts as @d_k_bo@feddit.de being broken whithout any possibility to change their URL.