The manual says C-c followed by a letter is reserved for users.  I
    always assumed that means C-c a through C-c z, but now Pat points out
    that there are also C-c A through C-c Z as well as nonascii letters.
    C-c ß, hmmm...

    Do we want to reserve C-c A through C-c Z for users, as well?

They already are reserved for users; the manual says so.
Are you suggesting we change that?  Do you think the manual
needs to say it more emphatically?