I would like to see the "No role for this user" setting for user permissions preclude the user from commenting. This tool could be used in moderating some commenters that do not necessarily need to be banned or their accounts deleted, just silenced for a period of time. I moderate a popular local blog and in worse case scenarios block IP addresses it has been my experience that some folks just require a little shot across the bow less prohibitive but do not need to have their account deleted.
Thanks for WordPress. Your work is greatly appreciated by many.