Comments in DW are a conversation, but the pace is different. Facebook (and Youtube even more so) is prone to immediate responses and often can become quite heated as a result, although LJ-dramas obviously existed. But even then it was relatively rare in comparison. A lot has to do with the sheer pace and volume of content I suspect. Which brings me back to that Slow Blogging manifesto; reject the demands of immediacy and treat words with reflection and importance.