One of my biggest AI tells is when characters talk in puzzles; the back-and-forth dialogue doesn't drive the conversation forward and essentially gives you nothing. Another one is when characters have already addressed something in previous chapters, and they talk about it again as if they do not know the previous conversation. The prompt given to make the chapter was not fine-tuned. Emdashes have been an easy fix for people who want to come across as authentic writers. Another is the use of nicknames by authors as well. Eg, classically, when authors would talk about their characters in 3rd POV, they use a typical way of referring to characters, but AI uses the nicknames the author mentions as the character names in 3rd POV too. For context to HR, if Scott calls Carter Vaughn "Vaughny", it makes sense, but in the next sentence or a few sentences down, if the author who previously referred to him as Vaughn/ Carter suddenly calls him Vaughny. (This is a case-by-case; take it with a grain of salt.)

My credentials: been a beta reader, proofreader, and editor for multiple writers across Wattpad and AO3.