The latter. It should have a direct and unique link as long as the post is online. Like Original Flavor Usenet, that might vary depending on the servers in question. But consider also the archive.org case - if they absorb Nusenet content in any form, structured unique links become of longer lasting value.

Yes, there is a part of me that is taking the approach of 'treat anything you put on the internet as there forever'. Because that is often more true than not.