How can I add comments to each job listing

This code in functions.php will enable comments:

add_filter( 'register_post_type_job_listing', 'custom_register_post_type_job_listing' );

function custom_register_post_type_job_listing( $args ) {
  $args['supports'][] = 'comments';
  return $args;
}

Creating a job currently posts jobs with comments closed – I will add a filter in the next update to get around this, so as of version 1.2.1 you’ll be able to use:

add_filter( 'submit_job_form_save_job_data', 'custom_submit_job_form_save_job_data' );

function custom_submit_job_form_save_job_data( $args ) {
  $args['comment_status'] = 'open';
  return $args;
}

Until then, after the first change, you can enable comments by editing the job itself.