If you changed to a different theme, does the comments label under the post title show up and also on the full post view?
I just now installed a fresh WordPress 3.7.1 and installed Celestial Reloaded 2.4.1 and I get the “comments” show up under the post title, plus when I view the post itself, the comment form shows. I then made a custom home and blog page, did the Settings >> Reading, where I set the two pages. Same thing, I get the comment label and also the form show.
So there must be something with your WordPress settings somewhere or perhaps a plugin that is interfering with the comments. Did you find any info searching in the WP forums about missing comment form?