Mark has the impression that what he used to call the Scandinavian hypertext blog cluster has vanished. The blogs are there, but the theoretical discussion has gone. I have thought the same thing.
I can only speak for myself, but I write less about theoretical ideas found in other blogs. Quick check: I haven't done so since March! I read other blogs than I used to, and probably fewer. Those I still read tend to have less theory in them, I think. (I think, and that's Mark's point, that we should try to find out.)
But I also do less theory work myself these days. My Ph.D. is finished, and I have been teaching and starting new projects. That is probably true for Lisbeth, Torill, and Jill as well. (I am reintroducing research work here these days, though.)
Many of us were curious to nail down what a blog is. I think that interest has cooled somewhat, and AoIR this year did at least satisfy that curiosity in my mind.
Mark is also suspicious if comments kill the slower discussion. Torill has had a version of that point earlier. It's hard to know. Although I think blogging is about quick writing, I do polish my posts more than my (few) comments. And I rarely read comments in other's blogs. It may be that Mark has a point.
Jill doesn't agree with Mark. That's OK. But I recognize the feeling he describes.