@dbraud:
You have missed the point of why quoting and/or post numbers are needed.
Quoting and using post numbers are not to address a specific reply at a specific person, they are to provide context to what is in your reply, which is after all going to the thread for everyone to see, not just that specific person. @user is a nice feature, but it in no way replaces the need for quoting or using post numbers.
Also, it is very common to have replying more than once to a thread. Simply specifying @user does nothing to tell me which of my replies you might be replying to - that is what quoting and post numbers are for.
I wonder sometimes how much time the developers have actually spent participating in large, active boards such as CC.