It's not clear to me if the law applies to forums or threads within forums.
I have found (here and elsewhere) that the longer a thread becomes, the more difficulty people have in remembering who said what, and opportunities for misunderstanding increase, along with the heat generated. I have wondered if Moodle's provision of different ways to view the thread contributes to this in long threads (though it is a useful feature). Perhaps social norms evolve to help matters, such as participants starting a new, related thread or choosing not to comment (a more general case of Godwin's law).
