Accessibility isn't just about screen readers.

Example user flow illustrating brokenness:

1. Open Firefox.

2. Disable JS.

3. Go to:

    http://www.avc.com/a_vc/2012/05/twitter-brings-you-closer.html

4. Follow the "View the entire comment thread." link:

    http://avc.disqus.com/?url=http://www.avc.com/a_vc/2012/05/twitter-brings-you-closer.html

5. The "Please login to view this page" dialog is missing any visible keyboard focus for hyperlink controls.

   http://www.w3.org/TR/WCAG/#visible-focus

6. The dialog includes a "Use OpenID?" link that doesn't lead anywhere. Not supporting some functionality without JS is regrettable and sometimes unavoidable; leaving broken controls in the DOM is just that: _broken_. Feature detect and add controls to the DOM when the necessary functionality is available.

7. Follow the "Go home" link:

   http://disqus.com/

8. No visible keyboard focus on the Disqus homepage either.

9. Click "Sign Up".

10. Click "Create commenter account".

11. There are big buttons in the page ("Facebook", "Twitter", "Google") that do nothing.

As a web developer who cares about frontend code and UI quality, this sort of thing is enough to put me off integrating with Disqus. Which is a shame, as I think commenting-as-a-service is a great idea.