I’m afraid forcing watermarking generated content is doomed to fail, for 2 reasons: first it has to be voluntary, second, watermarking can always be removed if one does not care about preserving the exact content.
Rather, I believe systematically signing original content may alleviate some of the issues created by algorithmic content generation.
What prevents you from revoking your payment mandate at your bank?
In Europe at least, your bank must honor this request and there’s nothing your debtor can do about except spending 1000’s to recover at most 3 months of payments with the current legal apparatus in Europe.