Zenqus: Universal Disqus Comments
Upon installing this script, you will see a button on the bottom left corner of the page on most websites. Clicking on that button will bring up a Disqus comments section for that particular URL. All comments are public.
It may not work on some sites (e.g. Github) and URLs that can change but show the same content will have different comment boxes as the URL itself is the identified for the comments. Basically, one youtube video viewed from two slightly different URLs will have different Disqus comment sections.