The client could tell a remote server when it forks a page. However we don't want strangers to write on any site (they will find a way to spam). However, a complementary notice could be ignored, counted or recorded. All are useful options at various states of growth.
Everything you wanted to know about forking. What is a fork? Why do you need to know? And why is it so beautiful?
An author may be very interested for a range of reasons in who has forked there work, or they may not. Both scenarios are important and should be respected. Authors should be in control and not the software.
There are a number of interesting Fork Edge Case, associated with some recent discussions (Nov 2013), concerning static sites and using separate data hosting. In both cases there is not an intelligent server component to do anything with such a request.