I'm on a french layout so I know :-) It also has the side effect of "resurrecting" dead keys (which are unrelated to Option), making input of 'ê'and 'ï' imposs

I'm on a french layout so I know :-) It also has the side effect of "resurrecting" dead keys (which are unrelated to Option), making input of 'ê'and 'ï' impossible. An alternative is using iTerm2 which has a similar setting, liberally applyable to either Option key.