Discussion Block Missing on Post/Page Edit

The entire discussion block is missing on all of my posts and pages. I'm talking about the area below the content that shows checkboxes for:

[ ] Allow comments on this post
[ ] Allow trackbacks and pingbacks on this post

Comments are enabled and the comment area is available on posts, and not available on pages. The options *do* appear in Quick Edit (!?).

The only thing below the post/page edit sections is SEO.

I've disabled all plugins. I've tried several themes. I tried a several sites in the network. It is the same for all. Any ideas?