Comments not displayed
Debugging is the art of taking away all possible causes ... in this case you want to make sure that the permissions are set correctly. so that for the user id you're using, it's allowed to post comments.

Not sure if it is "the" reason for your issue, but without appropriate permission Drupal seems to work as it should.

Another reason might be that you have "the field deactivated in the manage dispay settings of the related content type" (as per your comment below this answer seems to be your case).