some typographical quote characters in Courier are drawn as empty space on Mac OS
Can be verified by pasting some of this text into font sampler (some quotes do work):
„double quotes“ and ‚single quotes‘
U+2018 ‘
U+2019 ’
U+202A ‚
U+202B ‛
U+202C “
U+202D ”
U+202E „
U+202F ‟

Native Mac OS applications prove that these characters are defined in Courier.
In print they work.
With Courier New, it works too.
This is a critical bug for our software, since most of our customers write novels and tend to use Courier a lot.