RE: why does occur depropertize matching lines?

[Drew Adams]

        Most faces don't change background color.  Only very special faces
        (that are very rarely used in buffers on which occur is usually
        called) have background different from default.

    Yes, most such faces are used for temporary highlighting.

I don't think these assumptions should be made. Users can define faces (for
font-lock or anything else) any way they want, including changing the
background.

        > What we really want is to copy the face info from the source
        > but "dim" it a bit so it doesn't overshadow occur's own
        > highlighting.

        There is one problem with dimmed faces: they might be not readable,
        especially for visually impaired users.

    On some terminals, such dimming is not even possible, due to the limited
    number of supported colors.

I wouldn't want dimming, anyway.

Any highlighting that `occur' does should just be done without regard to the
highlighting already there. If it turns out that `occur's highlighting uses
face `foobar', and that is confusing in my context because I use `foobar'
for font-locking, I can change the face used for `occur' highlighting
(assuming it's not hard-coded!).