Indeed, as this page links to the comments made by the freeper with the number 100000. But you may have spotted that you were directed to the page:
http://www.freerepublic.com/tag/by:the100000thfreeper/index?tab=comments;brevity=full;options=no-change
(here you can spot the actual name), and that the page has the line Posts by The 100,000th FReeper! (again the freeper's name) in it.
Your title is still incorrect. Your premise isn’t who but how many. Page views answers that.
That really is kind of a side diversion as the main problem I have with your analysis is how you came up with the 28% variance in registrations and membership.