This technique generally (applying NLP to 10K’s and other corporate filings) has been in practice for many years. One common, highly commoditized text signal is

This technique generally (applying NLP to 10K’s and other corporate filings) has been in practice for many years. One common, highly commoditized text signal is earnings surprise: measuring sentiment in earnings call transcripts, and comparing sentiment scores with similar metrics from analyst publications in reaction to the earnings announcement. The arms race effect you mention absolutely exists. Corporate officers are often coached extensively on key phrases to repeat in earnings calls, and phrases to avoid, and how to steer caller questions away from SEO-like speech patterns they don’t want.