Yes there has been lots of bike shedding. A lot of people, myself included, have lobbied that ! in CSS is already an abomination (because in normal programming it generally means 'not').
Currently the discussions/draft/etc don't match or agree on what the syntax or capabilities will be.
Our :-hitch-has is based on the original :has proposal and the existing implementation in jQuery as we feel that this is the best (and clearly the most powerful since it allows you to express more).
There are plenty of free chars that wouldn't expect to cause conflicts with things like sass, or appear at a glance to be a variable reference.