Nothing is deleted from Hacker News unless the author deletes it themselves or asks us to. Everything else can be linked to. Hence my question.

If a post is marked [dead], only users with 'showdead' turned on in their profile will see it, but that's trivial to turn on, so anyone who wants to read such comments easily can. And of course users are free to vouch for [dead] comments, which in most cases promotes them back to normal status.

Since you've made many accounts on HN, presumably you know all this.