Yes, I agree with you, things can get out of control. That's because the other thing the sites with great conversations have in common is an element of moderati

Yes, I agree with you, things can get out of control. That's because the other thing the sites with great conversations have in common is an element of moderation and "etiquette". You can't take a random selection of people and expect their community values to spring from nothing. It has to be tended and moderated and standards have to be established, people have to establish reputation by becoming known among others. Threading and nesting and numerical reputation have an allure because they seem to allow you to skip all that -- let the math and the tech enforce a lowest-common community value. But, as I think we see time and again, that doesn't really scale and it doesn't engender great conversation on a par with the best of the flat forums.