Re: mode-line-inactive and face inheritance

[Richard Stallman]

    More specifically, it adds an `all' entry which (just like `t')
    always matches but doesn't prevent subsequent specs from being
    considered.

That seems useful.  `common' might be clearer than `all'.

                 Also it allows nesting of display-specific specs
    so you can extract the common part of the `light' and `'dark'
    settings for `color' displays.

That seems too complex; I think I would not want to document this
even if it worked.