LLMs are good at copy editing. They recognize when words are misspelled or grammar is poor very easily, despite not being able to see individual letters.
For understanding the guy's point it helps if you know anything about Heather Cox Richardson. Merely saying her copyeditors could be replaced by AI is a gross minimization, probably most of her own work could be too.
HCRs newsletter is popular because she delivers much purer, harder Trump Derangement Syndrome than anyone else on the market. That's it, that's the entire secret to her success. She delivers an ordinary and easily LLMable service (summarizing news), but ramps the Trump hate up orders of magnitude. Her competitive edge is she delivers to a market of liberals who find themselves disgusted with the mainstream journalism because, as they see it, it tries much too hard to be neutral and unbiased. It's sort of like how the Guardian makes millions off of donations by being a very openly left wing paper, except 1000x more extreme.
One might think US journalism is not particularly neutral, but they claim they are, so if you reject the whole notion that journalism should be unbiased as idiotic appeasement the market doesn't have much for you. Into this gap steps Heather Cox Richardson, a humanities academic who for a low low price will send you a daily news report that, every day, tells you how evil and bad Trump is and how good a person you are for realizing that.
Go read some of her reports and then tell us an LLM couldn't write them cold, I dare you. It probably wouldn't even need to be a big LLM. Summarization and rewrites are things they're really good at. She never even cites sources and hallucinations aren't the sort of thing her customer base are going to notice.
