Movable Type plugin – TrustedCommenters

MT has a great “white-listing” built in called TypeKey. Unfortunately, it requires your readers to sign in and sometimes readers just don’t like to do that. The side effect of this is that if your readers happen to trigger your spam filter plugins, then you’ll have to deal with readers that get pissed with stupid spam filtering instead of carrying the conversation on the blog.
TrustedCommenters changes that by allowing you to trust certain commenters depending on their user name, e-mail address, and IPs that the commenter comes in on. This isn’t the easiest white-listing type method but it’s definitely a start. Another great plugin by Mark Carey.