How to disable pop-up comments?

I know that I have to find this line in the header and add //

<?php //comments_popup_script(); // off by default ?>

After having done that, however, the comments won’t display on the regular page. When I click to view the comments it just takes me to https://MY-URL-HERE/WORDPRESS/2006/08/16/testing/#respond

That page contains the original post, but no comments. What gives? How can I fix this?