It's also the wording. The weird phrases

"Glorified Google search with worse footnotes" what on earth does that mean?

AI has a distinct feel to it

And with enough motivated reasoning, you can find AI vibes in almost every comment you don’t agree with.

For better or worse, I think we might have to settle on “human-written until proven otherwise”, if we don’t want to throw “assume positive intent” out the window entirely on this site.

Dude is swearing up and down that they came up with the text on their own. I agree with you though, it reeks of LLMs. The only alternative explanation is that they use LLMs so much that they’ve copied the writing style.