We have not performed tests with Disqus or IntenseDebate, but if there is a public API I believe that you will be able to integrate them with Sitefinity.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items