Comments have been re-opened.
As described here, WordPress has developed a bug where it periodically closes commenting on every post on the site. At this time, there is no solution and WordPress’ development team appears to be pretending that the problem doesn’t exist. The only solution right now is to wait for it to happen and then turn the comments back on manually.
If you come to the site and comments are turned off on any post, it’s an error. If it’s not too much hassle, feel free to drop me a quick e-mail so that I can fix it.
Thanks.