I have a similar problem with user rights. I created a group named special member by using User Groups and gave this special member group rights to post comments and other things. Then for registered users and visitors I put "no" to post comments. However, nothing happened. Registered users can still post comments. HoweverIt seems that user group rights do not work or I am simply missing something. Please help!Simon Wells (K2 Support) said:

Are you using the K2 Login module or the standard Joomla Login module?If you are using the K2 one, then there should be no issue.You may also be interested to know, that we have a mod to the commenting system, Auto Comment Notification.You, the admin, can be emailed whenever a comment is left on you site.Additionally, we also have a guide that removes the recaptcha for registered users that are logged in, they have already been approved, so why burden them with it.Any questions then let us know.SimonK2Joom.com