There are two reasons you might want to share the link to an HN discussion: if there is interesting discussion going on, or if you want to encourage people to upvote it.
In this case, there is no discussion about the article, just about the upvote brigade. So the only reason for sharing the link to the HN discussion would be to get people to upvote it.
Unlike a company where an employee just posted an HN, the majority of people in a discord community might not even know Hacker News is a thing, nevermind knowing someone posted something interesting on it.
Yeah, I have experienced that as well and I get your point, that's mainly why we have created a whole structure and registered an organization, even if we can never predict what will happen next we can always do our best to get the odds in our favour.
Unfortunately, the best alternative would probably be the P2P way, with something like https://matrix.org/ which also seems to be nice.
To clear that up a bit, you can register a channel like #domain.tld only if you control the DNS zone of the said domain, and you can't get op in a primary channel without registering it first.
Yeah. In fact, there is a lot of networks but they are made because people want to experiment and operate a server then they wonder what they could use it for. Here, well, we had a goal and IRC was a solution, as once you have your channel you just have to add an iframe on your website and tadam, a fully functioning live webchat with permissions! ;)