Comment by Jun8

This, of course, is a form of digital watermarking in for textual data. Due to unique problems, natural language watermarking and steganography is not advanced or is covered as much as image, video, and audio watermarking. For one thing, it is impossible to make changes to text that are udetectable by consumers, as in images; all changes introduce meaning shifts.

If you want to dig deeper, here's one of the rare introductory papers on the subject: https://www.cerias.purdue.edu/tools_and_resources/bibtex_arc....