Personal opinions follow.
It looks like the only actual use case we have, exemplified by the xkcd
strip, is for a star with the left half black and the right half white.
There *might* also be a case for the left-white, right-black star.
Everything else, including one-quarter and three-quarter stars,
rendering tomatoes or doughnuts or film reels as "glyph variants" of
stars, facilitating a right-to-left rating system for Arabic- or
Hebrew-speaking environments, or turning Unicode into a standard for
rating systems in general, is a complete flight of fancy by comparison
to Jörg's original post.
I think in this case, as in many others, one introductory, exploratory
proposal would be worth ten thousand speculative mailing-list posts.
--
Doug Ewell | Thornton, Colorado, USA
http://www.ewellic.org | @DougEwell