DISQUS is a popular "social commenting" platform. It is integrated with many hosted blog platforms and open source CMSes, including Drupal. A client of ours exported the comments from their old Wordpress blog and then imported them into DISQUS. The problem was that the comments were showing up in the DISQUS dashboard, however, when you clicked their corresponding URLs, these imported comments did not appear in Drupal. While the Drupal module looks for comments on the node/X URLs, DISQUS was storing them at the old Wordpress URL which were implemented as path aliases in this case.