My comments policy on my blog is pretty simple:
All rational, respectful comments are welcome on this blog!
There are two types of comments that are not welcome and will be subject to immediate deletion. The first are blatant link-gathering comments. If you post a comment that is only barely relevant to the article (or is not relevant at all) and immediately follow it up with a link to your own site, I will delete it. I have no problem with links to your own or other people’s sites, but they must be relevant.
The second category of comments that will be deleted are hateful, hurtful comments, clearly designed to stir things up. I welcome discussion and debate, so by all means feel free to disagree with anything I write. Tell me what you disagree with, and I will publish your comment and respond to it. But you must argue your point – don’t simply hurl abuse because you disagree.
For more information on my comments policy (and the reasons behind it!), see my post “Not welcome here.“