Jim, I hadn't thought of that, but I think I have never noticed it. I definitely pronounce words like "mountain" or "sentence" with a glottal stop in the combination "TN" and I don't include a schwa in

Not at all. Or barely in my experience. Perhaps when ... in 'à actionner' if you'd call that a glottal stop. Sorry. My French is not very good, but I do remember something like that. I'm interested now but I can't see

But I think your "oy" is what I know as "oi!", an interjection that I closely associate with white-supremacist Nazi skinheads, especially if they have Cockney accents. Time for some thread drift: in a novel I read recently by