Hmm, that should work. My $LANG is unset, 'Compose , c' gives me a question mark in terminal, in a 'LANG=en_US.UTF-8 terminal --disable-server' (the disable server is important if there is another terminal running) 'Compose , c' gives me a cedilla with the font (Deja Vu Monospace). But I might have changed the default (I think I only changed the size, but can't really remember), which font is configured in your terminal?