I block third party cookies and can read Disqus comments. It seems to be working exactly as you suggest because it warns me "Warning: A browser setting is preve

I block third party cookies and can read Disqus comments. It seems to be working exactly as you suggest because it warns me "Warning: A browser setting is preventing you from logging in. Fix this setting to log in". Unfortunately, adding an exception for disqus.com doesn't fix that in Firefox 13. Disqus can also be blocked by NoScript, Ghostery and similar/equivalent addons or plugins so maybe that's the reason, not third party cookies.