A guy named Roth wrote a post, that got posted to HN, about pg's essay on how to disagree. pg responds. Husafan starts a dialog with pg. There's a response back, clearly continuing the dialog, saying "I felt like I gave that aspect of his post the reply it deserved", referring to "my essay", etc. but instead of being posted under pg's handle, the response is posted by nickb.
A little further down the thread, user ncart makes the connection:
http://en.wikipedia.org/wiki/Bourbaki
Edit: someone else who thought about this (much) earlier:
http://news.ycombinator.com/item?id=152428