I am hoping to inform them? It does not appear their comments with attempted @mentions have informative replies, and posting a link to an archive domain will mean it's dead-on-arrival. Unless someone vouches and then comments on one of those posts, there isn't really an opportunity for a commenter to tell them.

I suppose part of your point is that they should be able to see that the post is dead; that regardless does not tell them why the post is dead. I'm also not totally convinced they can see that the post is dead. When an account is shadow-banned on this forum they can still log in and post but their posts will all be dead to everyone except them; naively, it is plausible to me that they actually cannot see that the posts are dead because they were DOA. In other words, even though the account is not shadow-banned, the domain might be.

Anyway, hope that helps.