Commissar was warned repeatedly about trolling, and since he showed no signs of improvement and no interest in doing so, the staff has banned him.
http://boards.straightdope.com/sdmb/showthread.php?p=14092460#post14092460
http://boards.straightdope.com/sdmb/showthread.php?p=14086418#post14086418
http://boards.straightdope.com/sdmb/showthread.php?p=14082033#post14082033