I like comments as much as the next person, especially when they agree with me. But that's the problem. When they simply agree, I don't learn anything, and, as the title indicates, the purpose of this blog is learning.
Sometimes, people do disagree and give a different perspective. Even in this case, they are likely to dash off their disagreement without chewing on it and thinking it through. So, I might learn a little, but not as much as I would from a thoughtful and measured response.
So, I prefer to use trackback (although see my note below on spam). Although trackback does not guarantee a more thoughtful response, it lends itself to one by slowing down the response time a little. Thus, trackback has the potential to create a more productive conversation.
Most bloggers prefer comments. Why? It's not for knowledge or learning as much as it is for the immediacy of comments that creates an illusion of community, with its attendant social relations. As Joshua Marshall (via Autono Blogger) wrote concerning blogging:
"In most hands, it's more a medium of exchange than reflection."
If blogs are mostly "a medium of exchange than reflection," even more so the comments they engender. That's okay for some purposes, such as business. However, when one's purpose is learning, the "okay" can easily undermine the "good." For this reason, at least for now, comments aren't enabled on this blog.
For those who want to understand how I came to this position, read my posts (all in the sidebar on this page), perhaps starting with my first post that framed this issue: Blogging to Confirm vs. Blogging to Learn. (The posts are in chronological order with the first post at the top.)
Although comments aren't enabled, I welcome trackbacks and emails. In fact, if you'd like to post a "measured response" on my blog, just email it to me, along with any bio/contact information you'd like to accompany it.
Note on trackback spam: I've read a few posts on the problem of trackback spam (for example, here), which does create difficulties of my preference for those with considerable traffic on their sites.