Default Font Size Quirk in Entourage X

Entourage v.X for Mac no longer has any support (it's an age thing), so this
is the last ditch effort:

Over the past week I've noted that messages I'm composing in plain text
(including this one) display as Monaco-12. This isn't that big a deal,
except that previously, they would display as Monaco-9, and my preferences
pane still shows Monaco-9 as the setting.

Switching the message to HTML and back to plain restores everything to
Monaco-9, but anything newly typed is again Monaco-12. As I'm typing this, I
find that copying/pasting text, pastes as Monaco-9, even though the original
is Monaco-12.

This has no effect of course on what the recipient sees.

I have trashed preferences files and font caches, but nothing has restored
proper display. (Surprisingly, one of the preferences files I removed didn't
even restore itself: com.microsoft.Entourage.plist)

Has anyone out there seen something like this before?

Thanks,
Michael