It's about what matters most: Knowing what's happening right now, what everyone is doing, what one is supposed to do next. Then, chronological team chat. Versus finding the best comments, e.g. when discussing a news article, or pro and cons about an idea.
We were using Slack at my last job, and it was great (now I don't like Slack any longer though, not after they added their weird threading. I like Zulip instead). Slack & Zulip = good sometimes, HN = good for other things.
Aha you have in mind a chronological "chat" / discussion, with threads? Rather than a best-comment-first HN discussion page?
If you use something else than Slack now, it'd be interesting to hear what that could be?