Continuing the discussion from Being a Heretic aka Going Back to Pagination?:
What’s so bad about a “chat room” topic, I asked?
I agree that mixing mediums is dangerous, but I think this notion creates a false dichotomy.
I think we agree on what Slack/IRC-style chat is for: short messages, intended to be shared synchronously with whomever happens to be present at the time. Chat history is ephemeral; unimportant.
Chat channels also don’t normally plan to “end.” You don’t start a #games channel and then stop the channel when you’re “done” talking about games. You especially would never say, “hey, the #games channel has been actively running too long; we should shut it down and create a new channel.” That makes no sense. You just keep the channel going.
(Maybe if #games gets too cluttered, you split it into separate channels, #board-games and #video-games, but then you still leave both of those channels running forever.)
As I read @codinghorror’s remarks, the idea seems to be that there are two forms:
- chat: synchronous short-form never-ending channels
- forum: asynchronous medium-form topics that conclude when they’re “done”
In a topic, we want to encourage participants to read the entire topic before posting a reply, unlike a channel, and that’s important to prevent the topic from going on forever and ever. We want the topic to reach a conclusion, to serve its purpose and be done. I think Discourse does a great job of encouraging good behavior in topics.
But as I thought about it harder, it seems to me that while forums are for asynchronous medium-form communication, they certainly can be used for never-ending channels, too, where the history is unimportant/ephemeral and we don’t even intend for everybody to read the entire channel history before posting.
For a notorious example, look at 4chan, where the history of a “board” is intentionally ephemeral. When you click on a board, once you scroll past the flashing ads, 
the first thing you see is a recent post. Not the first post in the board, but not the last post, either. Just a post, from earlier today. If you scroll down a bit, you’ll see more posts, and eventually you’ll see the most recent post in the board.
If we were all on IRC and we said, “this chat thing is nice, but I wish we had a website where we could post a few paragraphs instead of short messages; old history would still be mostly unimportant, but the expectation would be asynchronous messaging within a 24-48 hour time window, as opposed to just saying stuff to whomever is here,” I think it would not be wrong to call that thing a “forum.”
Certainly if somebody replied, “that’s not a forum, that’s really a chat room,” that would be a weird thing to say, because it’s obviously quite different from a chat room.
But it’s also really different from a “topic,” too. I think it’s a third thing. You might call it an “evergreen topic.”
Concretely, earlier today I filed a feature request to summarize the first N posts of large topics by default, which would significantly help with scrolling and performance issues on large topics. But perhaps we could go further by hiding old history entirely on certain threads, without summarizing, showing only the first post and the N most recent posts in chronological order. (We’d especially then want to let the author update their first post beyond the edit window, which is a big annoyance for mods on our forum.)
That way, if topics have gone on too long, we can end them, but if we want to run an evergreen topic, we can.
. Arbitrary plugins is an enterprise feature for our hosting. It’s difficult for us to dedicate internal resources to pure chat when it’s not really what we do and incurs an opportunity cost; it takes time away from working on other discussion features that have been on our roadmap for a while and definitely would deliver a lot of value to our customers.)