Am I correct in understanding that all of my posts will be permanently deleted if all the relays I was connected to when writing the posts are disabled?
Discussion
Not necessarily. Users can broadcast notes that you post to the relays they’re connected to. So for instance if I were to broadcast your note here, not only would it exist on your connected relays, but now also on mine. NIP09 addresses event deletion, but it is dependent on relays honor the deletion requests as to whether all copies of your notes actually get deleted.