In WP > Settings > Reading, "Posts Page" is set to a blank place holder page.
This page displays all posts correctly, but does not display the comments form under each post.
WP > Settings > Discusion > "Allow people to post comments on new articles" is ticked.
The theme does not use a single.php, or page.php, just a simple index.php file, which displays both pages and posts. The comment form does display for pages. Here is index.php: