There's a bug open in qemu bugtracker for several years already, https://bugs.launchpad.net/qemu/+bug/1038136 . The solution appears to be trivial (see also some background at http://blog.nielshorn.net/2011/03/qemu-and-brazilian-keyboards/ ), but the problem is definitely still here.
Maybe it's a time to address this finally? :) I don't pretend to understand any significant bit of input handling, so am asking people who are more knowlegeable in this area to take a look ;) Thanks, /mjt