I've found this several times as well. I googled something to dispute a comment in reddit, and google "confirmed" it as accurate, citing what the person said in that exact reddit comment.

Google has become the ouroboros

A few days ago I went looking for something music-related that I've been trying to find for a long time. Google's AI response confirmed it existed and described it almost exactly as I've described it in the past. It was then that I noticed the source.

It was citing my own old comment, here on HN, about that musical moment as evidence that it existed. That was surreal.