Good points. What I was attempting to measure was the relative measure* of rationalists on TV Tropes versus other nerd communities. The part of my thesis being tested is that no notable difference need be hypothesized to explain EY's perception of unusual rationality in the wiki.

(Was I mistaken to believe that EY thought TV Tropes was unusually rational compared to other nerdy Internet communities, as opposed to compared to other Internet communities, full stop? I agree that TV Tropes is nerdier than most of the Internet.)

* i.e. fraction of population weighted by intensity of participation.