At the time, I tested to see whether some other currency marks would work. The yen, the pound, and the cent all failed to display.
Examine that journal entry now, and you'll find that the Yen mark (¥) and Pound mark (£) display beautifully. As they do now in this very entry.
WTF!??! How and when did this suddenly get fixed!? My old journal entries are beginning to look like unwarranted whining. I'm beginning to look like a clueless putz because of it.
Dammit. At least the cent mark isn't working:
<-- see, nothing!
(At least for now.)