Basically whatever you do, you always do it on a copy of the stuff that is hosted on your local instance, which then mirrors updates back to the original. If your instance closes, all the stuff you did until then will still be preserved (as it is in the local copies of all the other instances), but you won’t be able to comment or post anymore (obviously).
As I understand it the source of truth would be the instance that the posts originate in, so would they be read only now?
Basically whatever you do, you always do it on a copy of the stuff that is hosted on your local instance, which then mirrors updates back to the original. If your instance closes, all the stuff you did until then will still be preserved (as it is in the local copies of all the other instances), but you won’t be able to comment or post anymore (obviously).