Yes, I Block Comments
In 2007 and early 2008, I went out of my way to block Ron Paulers from SPAMing the comment section of this website in their effort to drown out opposing opinion. Since my decision to oppose a local Tea Party group because of their willing and public acceptance of 9/11 conspiracy loons became public, the trend of Paulers SPAMing this site has re-emerged and, again, I have begun blacklisting commenters who are hell bent on taking our discussions away from the topics at hand.
So far, a total of 4 IP addresses have posted at least 218 pro-libertarian comments that have made personal, entirely off-topic attacks against myself (sort of expected), our contributors, and solid conservative Republicans. One Libertarian commenter even denied the holocaust, blaming the massacre of the Jews on the flu. Ironically, his same IP address also made several dozen comments under different names about his opposition to vaccines.
There are still a couple libertarian-minded folks that have not resorted to these pathetic shenanigans. They're more than welcome to continue posting comments, as long as they're respectful and on topic without using multiple identities.