The snippet you see at the bottom of the side column is a new feature that has just been added today. The "top commenters" list is there to encourage visitors to give their opinion on thoughts expressed on this website. The five commenters who contribute most will now not only be having their say about blog posts but also get links to their website or blog shown on most pages.

By the way, as people do share the same names, the counting is done by looking at the email address given with the comment. (This address is never displayed or used to send unsolicited email.)