Since we advertise app-emacs/gentoo-syntax in the devmanual (see URL), it should have keywords on the major architectures at least. So please consider adding your ~keyword. Test plan: <http://overlays.gentoo.org/proj/emacs/wiki/test%20plans>
Since this is an elisp package it should be architecture independent, and it has been extensively tested on amd64, ppc, x86, and *-fbsd. So if you like, you may mark version 1.8 as stable immediately. This will save you some work one month from now. ;-)
Just added ~sparc for now; will look at it more closely next week.
~ppc64
alpha/ia64/sparc stable
Marked ~hppa.