TFA is talking about C2PA, a regular signature in the meta data. A lack thereof means nothing, but if it's there, the false positive rate should be near zero.

Most critics of watermarking have no idea how it works. Yet there are valid arguments against (and for) it, but they prefer to be misleading

Yes, but I also think it will be trivially by-passable if you pass your output through another LLM. At least for text.

It might help catch students cheating, but not real spam-bot usage. As soon as platforms start checking for watermarks spambots will add anti-watermark passes.

Imagine telling someone they're wrong without providing any evidence or context.