Wikipedia has a cheat sheet of well-known tells for identifying generated text. (With an appropriate warning not to over-index on minor ones as absolute proof) https://en.m.wikipedia.org/wiki/Wikipedia:WikiProject_AI_Cleanup/AI_catchphrases
Wikipedia:WikiProject AI Cleanup/AI catchphrases - Wikipedia

Please stop sending me replies like "TIL I'm an LLM, because I do one of these seventeen things!" I WROTE TWO SENTENCES AND ONE OF THEM WAS ABOUT THIS
@0xabad1dea anyone who got good essay marks at school probably learned to do at least two of the Seventeen Things.
@fishidwardrobe @0xabad1dea definitely more than 2. Also native speakers of British English derivatives used across the commonwealth
@lilstevie @fishidwardrobe @0xabad1dea If you learn those rules it's as a super simplified model suitable for elementary school exercises, and for the sake of being able to meaningfully break them. Not because writing is supposed to look like that.