Also the concept of voting and strictly time-based decaying.
Even worse, the only person who might see it is the one person you responded to since it's in the profile comment feed, and a back-and-forth isn't very interesting.
This makes forums much different where each new reply bumps the topic into the eyes of any number of people who are online.
The upstream is wrong. Avatars and (ugh) signatures don't make a forum. Being able to converse over time is what does it. That's how you get to know regulars beyond spotting their one-off posts per submission.
https://www.talkyard.io/-32/how-hacker-news-can-be-improved-...
Because: 1) when you post a comment, the topic bumps to the top of the topic list. Like a normal forum. 2) inside the topic, people quickly find the recent comments, via the sidebar (as shown in the video "Finding new comments").
(B.t.w. agree that Reddit & HN feel ephemeral. I remember maybe 2 usernames here at HN, and 2 at Reddit, although having spent a lot more time here, than what I've done at Discoure's forum — nevertheless I remember many more people over at Discourse.)
The mentions there work nicely too, I never get swamped with inbox messages, you can only mention one person in a comment, so there's no @channel nonsense as with Slack.