[CentOS] wall and mesg and Xwindow

I read in another post this morning something that reminded me of a 
question that has left my pulling my eyebrows out.  How are broadcast 
messages enabled in X? 
I have found that
# mesg y
at a console will enable wall to post to that console.  And, by placing 
"mesg y" in /etc/rc.d/rc.local, messages will be enabled on all 
consoles.  But they're not enabled in KDE, neither in a pop-up nor in a 
terminal.  So far, I've been unable to find what changed between CentOS 
4 and CentOS 5 (and equivalent upstream versions, obviously). 

Would someone share a clue?