I came to appreciate typos, slightly ungrammatical sentences, and creative plays on common phrases. They are completely absent in LLM output without a specialized prompt (and they seem to struggle to make believable language mistakes even when prompted), so they can serve as a signal when judging whether the text I'm reading was written by a human.

As an aside, I observed my stance on proper English use changing in real time over the past 2-3 years. I used to be proud of writing clinically correct prose, and found mistakes in grammar and vocabulary grating. Now, I kind of welcome them and have stopped caring at all about committing such language crimes. I used to cringe when someone didn't capitalize the first words in their sentences - not anymore. I think we're years away from LLMs convincingly faking human-like mistakes (since all the work currently goes into avoiding them), so it's going to remain a useful signal for a while.