AI witch-hunts are definitely a problem. The only tell you can actually rely on is when the AI says something so incredibly stupid that it not only fails to understand what it is talking about but the very meaning of words themselves.

Eg,metaphors that make no sense or fail to contribute any meaningful insight or extrenely cliched phrases ("it was a dark and stormy night...") used seriously rather than for self-deprecating humor.

My favorite example of an AI tell was a youtube video about serial killers i was listening to for background noise which started one of its sentences with "but what at first seemed to be an innocent night of harmless serial murder quickly turned to something sinister."