[MlMt] New version broke fonts?

[Seebs]

So, plain text emails are now displaying in a non-fixed-width font.

This is not ideal. But I can't find a way to change it. There's a "theme 
for plain text emails is:" thing in preferences, which appears to have 
some very subtle effect on rendering.

Also, there's a "show fonts" button in Font Settings, but it does not 
appear to allow me to find out what font it thinks it is currently 
using, it only allows me to pick a font. There's no "undo" for that, and 
I can't tell what it was on before. And "reset fonts" goes to something 
which is also not what I was previously using for the message list, but 
I have no idea what I was using.

Mostly, though, I want to fix the display of plain-text emails.

-s