The comments_popup_link function is the last one defined within the comment-template.php. I did exactly as it says in the suggestion:
find “if ( is_single() || is_page() )” and replace it with “if ( is_single() )”, but it still doesn’t work.
Have there been any changes in the comment functions since this post was written that might prevent those links from being displayed on pages? Is it possible, one of my plug-ins is causing trouble?