It absolutely IS a safety/usability issue. That's the whole point of the hack. Anyone who has flown our old CRT display A320s on a bright sunny day trying to maneuver around thunderstorms or perhaps respond to a TA/RA knows this is a problem. You look outside at the white clouds or search for traffic and then when you come back inside you can't see a thing on the PFD or ND because they are too dim. I've heard, anecdotally, maintenance has been restricting our ability to brighten the display by dimming them internally to preserve them because, as you say, they don't make them anymore and so it's become a parts issue. But make no mistake, it is most definitely a usability issue and maybe even a safety issue as well. IMO.