There just isn’t enough information in plain text to do this and we should stop pretending there is.
If we need to verify something isn’t made with ai then we need other ways of doing so - eg looking at a document edit history, doing it as an exam, oral defense.
There are options! But pretending you can tell if text is ai will only catch out people who make no effort to hide it and will inevitably have false positives.
It seems it would get as simple as:
outputText = promptLLM(prompt)
scrubbedText = scrubWatermark(outputText)
Might help with students and low-technical people passing off work as their own, but any industrial scale slop-generator should be able to bypass it trivially.One could even say, the mark is load-bearing.