I'm not a native Japanese speaker, but I have been using AI to write 95% of each email in Japanese. I try to avoid using words which I don't understand.

I've gotten personal praise from many about how perfect my emails are, though the expectation is likely lower because I'm not Japanese.

I mostly use Claude for simple engineer-to-engineer communication, which has always sounded robotic, so I don't have much experience with long-form.

Chinese native speaker here. On Zhihu (known as Chinese Quora), I feel like every piece of answers are AI-generated nowadays. Although before LLM time, maybe 90% of content there are also meaningless. There must be some false positives, but I'm just becoming uncomfortable with those AI-like tones like "not.. but.." or something. I'm getting persecutory delusion on it.