I'm inclined to believe them too, so when he said he used LLMs to tweak the wording, I'll accept that was the case.

Perhaps the opening post was ill-phrased, but I think the second post clarifies it a bit: https://news.ycombinator.com/item?id=48677597 - and I was certainly getting some vague LLM vibes from the writing, so I was curious about this too.

So, whatever it is in the LLM output that is detectable, it's clearly detectable, even with the latest LLMs, and even when it's present possibly only in trace quantities.