Re: face cache referred to but not explained

[Richard Stallman]

     "This function clears the face cache for all frames.  If UNLOAD-P
      is non-`nil', that means to unload all unused fonts as well."

    The doc simply repeats the function name, without adding anything useful.

It would be useful to add a little about why someone might
want to clear the face cache.  I can't write it, because
I don't know the answer.

If nobody knows the answer, that is unfortunate but no disaster.