It had been a fairly long-standing policy that comments closed on posts older than 30 days.
After giving that some thought, I have decided to lift that ban. Much of my traffic is on older posts, so I shouldn’t preclude the possibility of intelligent discussion opening up on an old post.
So now comments are enabled site-wide, on both new and old posts.
Please read my updated commenting policy, and use this new freedom wisely. Enjoy.