Eli Zaretskii wrote:
> messages and documentation displayed in batch mode might be illegible
> on some text terminals.

Thanks, I hadn't thought of that, and overoptimized.  Easy enough to do the 
check even if -batch.  I installed the attached patch.

> How is the locale's codeset relevant here?  The issue was encountered
> in a GUI session, where that should be unimportant.

Yes, but the bug was that Emacs hadn't initialized the GUI yet and so 
char-displayable-p acted as if in a tty session.