Well do they? It doesn’t matter much to me either way, but I am kind of curious. If Pster X joins as a guest for a month, and then decides to join will his post count be 1, or however many posts he made while a guest?
Yes, post counts will carry over. As will Karma and Nanju.
Yes, I made up Nanju. 
Yep… Try viewing the Guest’s profile and you will see their post count. 