Re: BUG [Emacs 21.1] face property ignored on some minibuffer prompts

[Richard Stallman]

    In Emacs 21.1, when reading input from the minibuffer using the
    following functions, the face property on the prompt string is ignored:

      y-or-n-p
      read-char
      read-char-exclusive
      read-input
      read-key-sequence

That is because they don't use the minibuffer--they just read events.
So they use a different mechanism to display the prompt string.
It is just an echo area message.

In principle, an echo area message ought to be able to support
displaying faces.  Now that the echo area message actually is
displayed from a buffer, it might not even be hard.  Would someone
like to debug why the faces get lost in the process of displaying
an echo area message?