"precious few threaded discussion models survive on the web."

Citation needed. Seriously, you can't just casually throw out a phrase like that and not expect to back it up. HN seems to be going fine. Reddit seems to be going fine. Facebook has threads now I've noticed and it hasn't exploded in a ball of threading-related fire. I can't think of a website that has died because it uses threads, nor can I think of a website that is overly popular because it doesn't use threads.

Anyway. let's talk about his arguments a little:

1) It's a tree. His argument seems to be it's unnatural and confusing to read. This is sometimes true. What's even more confusing though, is when people wish to reply to one particular post, but since it's flat it all gets smushed together into some kind of massive confusing shouting match.

2) Where did that reply go?

- "How do you know if there are new replies?" Yep, that sucks, no question there.

- "reply at the wrong level" I'd argue that occasionally getting your reply wrong is better than constantly replying into a shouting match and never being heard.

- "responses buried somewhere in the middle" that kind of thing is lame totally, but it can be "fixed" (to a point obviously, imo, ymmv etc) with a upvote system

3) It pushes discussion off your screen. Aka "indentation is ugly". That is certainly true, but it can be mitigated (at least in terms of wasted vertical screen space) with expand / collapse buttons. In terms of horizontal space, I think that's an UI issue waiting for someone to solve it (I don't think it's a fundamental failure).

4) You're talking to everyone. Not sure what he's really talking about here, I don't think anyone thinks a reply to a comment is private-- you reply to an existing comment when you want to comment on the comment, not talk to the person who wrote the comment. Otherwise "polluting the tree with these massive narrow branches" seems to be #3 again.

5) I just want to scroll down. Basically, he finds it too hard to navigate in tree-space. The problem with this is that everyone else wants to reply in tree space, so even if your site has flat comments people still going to use @originalCommenter at the top of their comment, or if you're lucky quote the originalCommentor's post. And then originalCommentor will quote back, and so on and so on until, surprise!, you have threaded comments again, except this time it's adhock, ugly and with no collapse button.

I'm also confused as to why Jeff includes a couple of paragraphs implying that Stack Exchange is a good commenting system and then says "but remember: Stack Exchange is not a discussion system.". So then why bring it up? It not being a discussion system implies that perhaps the techniques used there may not actually translate into something that is a discussion system.

In the end, I understand that there are elements of threaded discussions that are frustrating, of course there are, nothing is perfect. But I would argue that flat discussions are, for certain types of conversations (specifically those had on HN and Reddit), far more detrimental. I'd go so far as to say that Reddit would not be even remotely as popular if it had a flat discussion system.