Netgen Comments is an eZ Publish extension that builds upon existing eZ Comments extension adding AJAX commenting capabilities.
It supports all of the features that eZ Comments supports: adding, editing, deleting comments, recaptcha, turning off unneeded fields etc.
Netgen Comments is built on top of eZ Comments, so it requires installing it. All the configuration is done in eZ Comments extension, Netgen Comments uses already available settings and honors them.
You can check out and download the extension on it's projects.ez.no page.
Source code is available on GitHub.