Why I have comments here
Recently I read Comments Off (via) and what struck me about Matt Gemmell's framing of the issue is that he seems to view having comments as something that you do for your blog's readers. What this says to me is that Matt Gemmell and I have significantly different views of comments.
Let me tell you a little secret: I don't have comments here for my readers, at least not primarily; I have comments here for me. If that ever was to change, if I stopped feeling that comments were a benefit to me instead of just (possibly) my readers, then I'd stop having them (either quietly or not).
(If I had comments primarily for my readers, I would probably structure things here to make them more prominent.)
There's several ways that comments are a benefit for me. To start with, I enjoy reading them. People's comments here teach me things, they give me ideas, they correct my mistakes, they keep me on my toes and in general keep me honest, they're periodically entertaining, and they make me change my mind every so often (that's a random example). On top of that, I have received a few comments that are hugely valuable in their own right, to the point where I feel they have pretty much justified the entire effort to implement and manage comments here all by themselves.
(As examples, a comment led me to pca, which has for years been the only sane way to manage patches on Solaris. Another comment introduced me to dmenu, which in less than a year has significantly changed how I use my long standing environment. Both of these changed my computing life for the significantly better and I doubt I'd have found either on my own.)
If you don't feel that comments on your blog are there for you, if you're really only supporting comments for your readers, then I tend to agree with what Matt Gemmell says. I think that it's hard to arrange a setup where comments really benefit your readers, and doing so takes a lot of work and a certain amount of luck (plus you're probably going to have to become a community manager in addition to a blogger). In today's world, not supporting comments in this situation makes a lot of sense.
(To be very clear: I don't think that comments here degrade the experience for my readers. I just think that they're probably a neutral thing because I expect that most people don't read comments. And I can't expect them to; unless you go to a lot of effort to build a community that people find appealing, people generally are going to be coming to your blog because they want to read your writing, not other people's. (And I am no exception to this.))
However, as I've written before I do feel that there are practical reasons that people like comments, although maybe those reasons are lower in the modern web of Twitter and Facebook and so on.
(Matt Gemmell is clearly aware of the downsides of his decision, as shown by the followup email exchange he has at the bottom of his entry.)
Sidebar: an honorable mention
In the 'comments that justified having comments' category: if I read weighty things more promptly I would be able to count the pointer to Russ Cox's first article on regexps that was left here. Instead I only read the whole series when the second and third parts appeared a couple of years later and made Hacker News.