I do not foresee this happening. The moderation and voting would require a significant level of trust of the other instances, admins and moderators. Being associated with other multi-media sites introduces legal risks I would be surprised if a VC was willing to take on. Assuming you mean a bi-directional integration into ActivityPub
That said one could run something like HN and moderate it independently. Maybe Postmill [1a][1b]. There are other sites that ingest data from HN's API [2] for search, statistical analytics, etc... Something similar could probably be done that would be ingested read-only into ActivityPub from another site but I would be quite surprised to see this site implement ActivityPub directly. I don't know what the API rate limits are for this site or if Mastodon could operate within them.
[1a] - https://postmill.xyz/
What's missing is comments from AP being ingested/posted to HN, the upvote/downvote federation story, and the moderation story.
Has @dang commented on this question in the past? Has anyone shown a potential HN source patch?
Where is the HN source code right now? Free and Open?
Yes and no.
HN itself is running a proprietary fork of Arc Lisp, which you can find here[0]. The Arc maintainters don't take public PRs or feature requests, and HN itself has numerous changes to the codebase which aren't public for business reasons.
There is a public fork of Arc called Anarki[1] which has no direct connection to HN or Arc Lisp, and for which the community and development is... well... anarchic.
And given the general culture here around minimalism and stasis (not wanting to introduce new features for fear of entropy that would negatively affect the signal to noise ratio and push the site towards Eternal September) chances are any large, publicly visible changes to the codebase aren't going to happen. People here riot if they change the stylesheets just a bit too much. Heaven help us if something imports content from beyond the AT field that Hacker News keeps between itself and the unwashed masses.
But dang's email is at the bottom of the page if you want to ask him.
Honestly, as with most such questions regarding HN, the preferred answer is probably to just write a third party client that uses the HN API and let HN stay what it is.
As strict as it seems, history seems to have vindicated this policy.
I'd start with that, and then just build something that spins out feeds of each user.