Or you could use a browser extension to open these links on archive.is automatically.
But, is it against the rules to directly post archive.is links of pay walled articles on HN?
It is discouraged in the guidelines. But you can also post a paywall bypass in the comments of your own submission if you would like.
> "Please submit the original source. If a post reports on something found on another site, submit the latter."
https://news.ycombinator.com/newsguidelines.html
> "Don't wait for someone to post the link, just go to archive.is and paste the NYT link there yourself."
Yes and also paste the link back in the thread for other readers! I see it as sort of maintaining the commons, a very simple courtesy to others. You spend two extra clicks yourself to save hundreds or thousands of clicks for others.