This is fascinating. I had never heard of this mark. I consulted with the typography bible, Robert Bringhurst's Elements of Typographic Style, and there was no mention of it which surprised me. I have an older edition of the book, so did look up references and found it referenced in the glossary description for glottal stop, which he says is a "sound in search of a character." I'm curious to know what the mark used in Mi'kmaq specifically is, and how it came into use. (I am assuming it is what is typographically referred to as a prime that has an increased point size?) I will have to do some more digging. Thanks for sharing this!