Of his most recently posted articles: Undiscriminating Skepticism scores at a Flesch-Kincaid grade level 17 and a Gunning Fog index of 17.9,

"Undiscriminating Skepticism" -- why, that's ten (10) syllables right there in the title! My head is already spinning!

Seriously: tests like those do not control for the content or subject matter of the writing. There exists, furthermore, a significant subset of the (adult!) human population who would consider a phrase like "undiscriminating skepticism" itself to be difficult and unusually abstract. Needless to say, tests which heavily weight the judgements of such people are not very useful for the purpose of judging "readability" in most contexts here.

If you want to judge the readability of LW posts, I suggest spending some time reading typical articles published in academic journals.