No Comments on Permalinks

Since upgrading to 1.5, the comments popup link does not appear on any permalinks. It appears as it should on the homepage, as well as on pages that are archived by date (like this one), but not on pages the permalinks.

Compare this to this. These are the exact same pages, the only difference is that the first is the dated archive you arrive at by, for instance, clicking on that date in the calendar, and the second is the permalink that you arrive at by clicking on the post’s title. The dated entry shows a comments link at the bottom, and the link pops up the comment window, as it should. The permalinked entry shows no comments link, and there’s not way to add a comment or to view comments that have already been added.

What’s going on here? I really would like comments to be enabled on my permalinks.