Well, a friend and correspondent recently shared a guideline concerning his own blog comment policy -- overall, he only publishes comments that add to or preserve the "feel" of the post, which he regards as primary.
The guideline resonates with me because it addresses motivation -- and motivation is key. All bloggers are driven by certain motivations when they sit down to write a post. Likewise, everyone who comments on a post also harbors their own set of motivations.
In my experience, the best comments are those that align with the overall motivation of the post in question. This does not entail that the comment must be "nice" or agree with the views, ideas, or content expressed in the post, but the motivation behind the disagreement should strive to add to or, at the very least, maintain the "feel" or atmosphere of the post.
For example, if I write a post about some aspect of Jesus or his teaching, I open to hearing from those who may hold different interpretations -- sometimes quite passionately.
I am not open to hearing from those who snidely accuse me of worshiping a "dead kike on a stick." The former may add something insightful, meaningful, or valuable to my post and adhere to the overall atmosphere of the blog; the latter will do none of these things.
Nevertheless, I have, on occasion, published some snarky, hostile, or poisonous comments. Sometimes I failed to detect or misinterpreted the snark or hostility. Sometimes I simply wanted to hear the person out. At other times, I wanted to respond to the hostile comment with a little hostility of my own. Whatever the case, publishing such comments has never led to anything good, and I always regret it afterwards.
From a broader perspective, the matter of comments is directly connected to the ultimate motivation and purpose of a given blog. In my particular case, I have come to the realization that this blog -- which started out as a halfhearted means through which to promote my novel -- has become a sort of open journal through which I attempt to log some of my spiritual learning.
More than that, it has become a way for me to share this learning with those who may be interested. The blog also allows me to connect, communicate, and relate to others who hold or may hold similar motivations, all without having to wade into the dreadful and often poisonous world of "mass" social media.
Furthermore, I tend to regard blogs as extensions of thinking. Anyone who has read this blog knows I regard thinking to be man's most important activity because thinking is ultimately reality. Of course, the thinking expressed on this blog via posts and comments is already once-removed from reality -- but I console myself with the idea that the expressions are at least pointing in the right direction.
And that's what comments boil down to for me. They have to -- at the very least -- point in the right direction. If they don't, they're not real. And if they're not real, I'm not interested.