Whilst poking around in ~/Library/Preferences/com.apple.mail.plist, making PreferPlainText equal “Yes”, I came across a property I don’t remember seeing before: “TornOffToolbarIsHidden”, set to Yes. Changing it to No and relaunching Mail doesn’t appear to change anything.
Googling “TornOffToolbarIsHidden” and “TornOffToolbar” don’t produce any hits. Has anybody seen this before?
I am envisioning nonexistent control palettes floating around.