The other person (at the top of this sub-thread) did say "Both of these points considered, I disagree entirely with the premise. There can be value to dense, even perhaps enigmatic writing. I would say that the greatest works of English literature tend towards that direction (James Joyce, Thomas Pynchon, David Foster Wallace)." I would not consider these edge cases, because I don't think literature is relevant to the essay and its purposes.
If you want to restrict Graham's argument to non-fiction, I'll happily grant you that.
But let me give you a bit more context:
As a Frenchman, when I think "Essay", my mind almost automatically reaches for two authors: Montaigne and Pascal (e.g. in his Pensées).
"Simple" is probably the last qualifier I would use to describe their works. They're not simple. They're complex, rich, beautiful, copiously quoting from classical authors and yet often crystal clear. They have the same quality poetry has where replacing a word by another damages the precision of the message and images conveyed.
That is also true of non-fiction prose in longer form. I shudder to think what could become of Tocqueville's writing style, a peculiar mix of classical and romantic, if it were translated into "simple" language.
