⌘-F "Godwin" shows me seven usages in this thread. I was looking for something like "see, Godwin was right". One commenter seems to have gotten it right. The rest think it's something one "invokes" (to quote one usage). Godwin's law is like the law of gravity: it always existed (in Godwin's case, post-WWII, obviously), whether you "used" it or not. You drop an apple, it'll hit the ground. An online discussion (or probably any discussion) grows longer, someone's going to make a Nazi comparison, which this article seems to confirm.