Look at the text of Pullum and Ladusaw, p. 211. All those x-height forms are simply glyph variants. If someone is taking the cap-height form and *distinguishing* it as a capital letter, then fine, come up with a new encoding for it, but don't mess with the basic glottal stop itself.
How would you like to display that in the code charts? This seems worse, much worse, than the INSULAR G that you didn't like.
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Michael Everson * * Everson Typography * * http://www.evertype.com
