It seems like the recent trend has been toward publishing blogs without public comment sections. For one thing, people are sick of spam, Internet cranks, and the work required to have a comments section that adds to the site rather than detracting. As an example, here’s Matt Gemmell explaining why he turned off comments. At the same time, many writers are using static publishing engines or sites like Tumblr that don’t even support comments. (I know you can use third party commenting tools like Disqus, but most people don’t.)
Here’s a chart that shows the comments per post broken down by month going back to the first month that I added comment support to the blog. As you can see, the number of comments per post has dropped, even though I’m publishing fewer posts. That said, the variability has been pretty high, and the months with high averages are a result of extreme outliers – blog posts that got tons of traffic and comments. A real statistician would also share the standard deviation for each data point.

So I think that not only has publishing a blog that includes comments gone out of fashion, but commenting has as well. It’s easier to link to a post from Twitter or Google Plus and just discuss it in those venues, or respond to the author of a post on Twitter rather than in the comment section. I understand the impulse, but these venues are especially ephemeral as compared to blogs or even blog comments.
I used to be pretty reluctant to comment on blog posts on other blogs, but these days if I have something to say and I’m not going to write a post about it of my own, I generally post a comment, especially if the publisher moderates the comments effectively. I do this because I see it as a way to signal my respect for the writer. I also think it’s more social.
Those of us with blogs have also always had the option of responding to posts on other blogs with posts on our own blogs. The upside is that you hopefully deliver some readers to the blog you’re linking to. The downside is that unless the writer links back to you, your commentary is probably lost on everyone who finds the blog post that is the subject of your comments later.
Maybe it’s the Twitter effect, but I find that I crave more discussion when I post something. Looking at traffic numbers is far less interesting than having a productive or enlightening discussion. For that reason, I hate that commenting appears to be on the wane.