...Terminal seems to have a built-in "safety-valve," because in addition to control-C, control-option-C and control-shift-C will kill a process.
I don't think so. I think that the extraneous keystroke had the effect of suppressing the launching of Calq (since neither Control-Option-C nor Control-Shift-C were the key combo to which you assigned that function); Terminal regarded both Control-Option-C and Control-Shift-C as Control-C with an extraneous keystroke—just as it does for me.
