One thing I miss about HN type forums is the "here is what you haven't read yet". When an article has 100 comments and I've already read 75 it is rarely worth my time wading through to see the new ones. Even though I know from experience that writing a good insightful comment takes a lot of time. Most of what I'm missing will not be very insightful, but I'm sure I'm missing some of the most insightful comments. It also discourages me (and I assume others) from writing a long insightful response at times because I most of the people who would be interested will see it.