Commenting privileges are restricted to those who come here to learn, to discuss, or to share facts and logical arguments in good faith in order to inform or persuade other reasonable citizens. (yes, this sounds pretentious; please help with the rewrite!)
This means civil discourse only; no ad hominem attacks, no "sneering tone", no wild accusations, no unfounded assertions. Focus on the ideas, not the people. If you state something as fact, back it up with a link to where you found it. If you're asked a question, answer it, or explain why it's reasonable not to.
Usual disclaimers apply: Don't post libel, this site bears no responsibility for what does get posted, but posts that don't meet the site owner's standards for reasonableness will probably get taken down. And, to crib from Joel:
All commentators are subject to blog policies whether or not they have read them. These include, but are not limited to insults, vulgarity for vulgarity's sake, libel, slander, ...posting off topic, etc. You are bound by my rules (guaranteed by my right of association and private property) whether or not you take the trouble to read them.
If you make a comment that's not inflammatory, and it silently disappears, don't assume that this was the result of a deliberate and malevolent act. The commenting system is a free third-party add-on of unknown reliability - and, given that email itself is unreliable these days, there's no guarantee that reliability of comments is any better. Please do send me an email if you notice it happening, just so I know that it really is an issue.
And if you comment on a post from the past, be forewarned that it may get overlooked.