The following KB articles relate to this topic:
Disqus is a blog commenting service provided by Big Head Labs. It allows users to leave comments on blog articles to be addressed by admins of the site. You can decide whether you want comments to automatically appear below your posts or if you would prefer them to go through a workflow process whereby an editor can either approve or deny the comment.
If you are interested in incorporating this functionality into your site, please contact us (external link).