A few months ago I took up historical fencing as another hobby, and it just occurred to me that the threads on a lot of the newer online forums -- places like Reddit and HackerNews and Slashdot -- kind of resemble the main stages of a bout in fencing: lunge, parry & counterlunge, parry, stop. In threads in these forums, it most often looks like: point, counterpoint, counterpoint, conclusion.
Of course, there are exceptions. Reddit has its pun threads which turn the whole process into a novelty. The other major exception is when a thread becomes heated; two or more participants suddenly become invested in the conversation, and the more argumentative everyone is, the deeper the thread will go.
Otherwise, people just aren't motivated to have anything resembling an actual conversation on these forums.
What's wrong then?
Assuming that the hypothetical "ideal" online forum wouldn't work this way, what's wrong with the current iterations?
There are more opinions on how such forums should be run than experimental data, so I think we'll just have to wait for other people to try out their own solutions, and see how all of them work, rather than offering up more opinions on the right way to do it. But, I do think there are some obvious common traits in Reddit and HackerNews, and that these traits won't be shared by the ideal forum:
Karma: By placing a score on each comment and accumulating that score into a total for each participant, forums become a contest, or a game. It's unavoidable: no matter how consciously someone tries to ignore their score, they will still be motivated to make comments which will get a higher score. It seems obvious that this is what these forums want: a way to publicly sort comments in some fashion so that the best rise to the top, but quality does not necessarily beget a higher score, and in normal conversation, not every single thing said is pithy, witty, insightful, brilliant, or otherwise worthy of accolades. But, without the mundane nuances between good points, you stop having a conversation and start having a game.
Sorting by score: The score on each parent comment in a thread then contributes in some way to its position in the thread. We already know that readers online will "skim" web pages, reading stuff at the top but not at the bottom. So, if you're a frequent commenter on an online forum, you don't want to put much effort into a comment that will languish at the bottom of the page.
Sorting by newness: This is a manifold problem: threads tend to be short-lived, and newer comments tend to find their way to the bottom of the page. I would guess that the maximum lifetime of a thread, within two standard deviations from the norm, is about one day. After that, the item that spawned the thread falls off of the front page, few people read it, and fewer still add to it. That leaves one day for everybody to make their points on the topic, which precludes doing anything in the way of serious computing or research. The later that someone adds to a thread, the less likely their comment is to be read or have its score increased; the game then rewards the people that spend the most time on the forums, that are in a position to add to threads while the thread is still brand new. They are also motivated to leave their comment, and then not return later to continue a conversation about it.
Conversation-by-crowd: I've noticed something interesting on Reddit: in threads with lots of activity, if you ignore the usernames making comments, you see something almost resembling a conversation. Then you look at the usernames, and you find that they're all different. People are essentially making or defending other people's points; person A makes a point, person B responds to A, person C shows up and makes the counterpoint on A's behalf, and so on. As online forums attract more people, this phenomenon happens more frequently, and again, you end up with something looking less like conversation and more like a fencing pit.
Noise: The "noisier" a thread is -- the more activity it's had -- the less incentive there is to participate meaningfully in it. Because of the other factors combined, anything you add to a noisy thread is less likely to be read or rewarded in any way.
Older-style forums did some of these better than the newer ones. Anybody could "bump" a thread to breathe life back into it for a day and threads could stay active for many days, or even weeks or months. You tended to get a lot of effort on a particular topic in a thread, so that the thread became a resource for other people later looking for information on that topic. You still see this in a lot of the online forums for cars, for example. If someone asks a question about some engine, and you see it the next day, and it takes you three days to find the answer and take pictures for the person and everything else that constitutes a high-quality reply, you're still motivated to do it because when you do, the thread will become active again.
If newer forums worked that way, and I were hosting such a thing on my site, someone might read this and, a month from now, post a series of graphs after accumulating data from various online forums.
And maybe that could lead to some good conversation.