We ask people not to submit archive links* because it's important for readers to see the original provenance of the article, e.g. in the site name displayed to the right of the title.

"Please submit the original source. If a post reports on something found on another site, submit the latter."

https://news.ycombinator.com/newsguidelines.html

* If the original article is really not available anywhere else on the web and is interesting enough for a good HN thread, posting archive.org is ok.