Earlier quoted context omitted.
Google has A/B tested watermarking on millions of responses. They say they observed no difference in user behavior.
It says they observed no difference in people clicking thumbs up or down. There are loads of other behavior that they didn't observe; like, say, switching to a different LLM.
Also, depending on what I am asking it, I often don't want to use the thumb down or up, as this may mean my conversation is going to have some kind of human review and depending on what I am asking for, I may not want to bring attention to my stuff.