@Josh - debating corners aside, you're right that the HuffPost model isn't the only one and I'd never say that it is. (and, for the record, these views are mine alone etc etc)
Now, to your point that "No comments does not equal no discussion." Definitely - people go where they can find good conversation, but if you believe that there's discussion to be had, why would you intentionally push it away from your site where it could spark new ideas, add to other readers' understanding of the issues, and possibly inform the original article or lead to new ones?
But, that is what makes Branch great: it's about conversation, not "comments" and you can easily create good conversation to go to if a site shuts it down.