I agree, HN is an amazing community with brilliant people and top quality content, but it's not enough to train an LLM.
Last thing. An LLM is just a tool, it can clean up your writing the same way a photo app can enhance your pictures. It took a while for people to accept that grandma's photos looked professional because they had filters. Same will happen with text. With ChatGPT, anyone can write like a journalist. We're just not used to grandma texting like one, yet :)
That said, this feature doesn't sound like a great leap for mankind.
Minus the fact-checking, transparency, truth and social responsibility.