This is a Role Scoper issue.
When using custom post types, Role Scoper causes comments to not show up, unless you're an admin.
I traced back this issue to hardway/hardwa-front_rs.php line 62:
$query = apply_filters('objects_request_rs', $query, 'post', '', array('skip_teaser' => true) );
The parameters 'post' is the cause. Passing an empty string fixes the issue. Not sure what the side-effect are.