In the new baselayout-1.12.6 the place where the variable DISPLAYMANAGER can be set has been limited to /etc/conf.d/xdm. Well done. But in /etc/rc.conf is written NOWHERE that now the right place where to set that variable is /etc/conf.d/xdm. No comment in /etc/rc.conf no info at the end of emerge. This could cause a very unhappy experience since IF you use kdm and kdm was set in rc.conf but /etc/conf.d/xdm is left untouched to the default value, that is xdm, next reboot the system when it'll be the time to fire up the xdm daemon, will fail because on that system no xdm is present. And this could be very unpleasent, especially for not so experienced users who fear bash. Please add a comment in /etc/rc.conf where is written that DISPLAYMANAGER now can be set only /etc/conf.d/xdm and maybe add even a message about it at the end of emerge. Cheers
in the future try to be a little less dickish added comment to 1.12.x branch