No but there was a user called nickb that was responsible for a disproportionate amount of content (excellent content) back in the day. There was a lot of speculation that nickb and pg were one in the same. Here are some posts for context:
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://news.ycombinator.com/item?id=99923
http://news.ycombinator.com/item?id=292858