Another useful metric might be the average number of comments per blog post, or comment intensity. The table below shows the comment intensity for five blogs: this one, dy/dan, Weblogg-ed, Cool Cat Teacher, and Ewan McIntosh's edu.blogs.com.
Charting the results shows the big spikes that Weblogg-ed and Dangerously Irrelevant had for two recent posts:
As the table shows, a large readership total doesn't always correspond to a high comment intensity (at least in this small sample). dy/dan has the lowest Technorati rank/authority but its median comment intensity over the past twenty posts is right there with Weblogg-ed...
What's your comment intensity?