Sites like HN apparently follow an unwritten rule that says there can only be one official URL associated with a post. Maybe that rule doesn't need to be follo

Sites like HN apparently follow an unwritten rule that says there can only be one official URL associated with a post. Maybe that rule doesn't need to be followed. Maybe it's just a common pattern sites follow, and it can be tweaked. There could be official metadata URLs such as cache links or non-paywall links, that appear alongside the main links. Certainly you've thought of this and some of the possible dangers of doing it: For instance, there could be blowback from sites if they think you are systematically circumventing their attempts to charge for content. But perhaps some mild flavor of it could be done, to address a subset of the use cases. For instance, content could be cached privately by HN, with the cache link hidden at first. Then if the content became unavailable, depending on the reason for that unavailability, HN could reveal the cache link or not, based on HN policy about which reasons for content unavailability are cases where it is desirable to provide a cache link.