We'll create fresh WordPress site with Disqus Notify Post/Page Author installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin notifies post/page author by email of comments posted through the
Disqus Comment System plugin even if the author is not an admin of the Disqus account used for the site.
In other words, this plugin implements the same notification functionality that WordPress ships with out of the box but which is disabled by using the Disqus Comment System.
Confirmed to work with (and to also be needed with) at least Disqus Comment System versions 2.74-2.84.
These sites/blogs describe the same issue that this plugin solves. Using this plugin is simpler though and prevents you from shooting your own leg (by not doing custom hacks)
Contributers to the initial version of this plugin that was released in March 2014 on GitHub