If the headrests bothered me, I'd probably do this. devbolt has a point, but I always wonder how older cars (made after 2000) still have luxury headrests that telescope and tilt. I'm doubtful a 30 deg change wouldn't be that deadly to whiplash from rear crashes. Like BoltinAround stated, the head restraints are still there. You might get more neck fatigue as your neck has to slow your head first before it slams into the head restraint to stay moving along with the rest of your body (and the car).
Useful info incase someone really hates the headrests. Sure beats someone turning the head restraint around where it no longer locks into the seat.
2017 Summit White Bolt LT, VIN #83351, built 8/2017 (real range anxiety now).
2017 Kinetic Blue Volt LT, VIN #11925, built 6/2016. (loved it, only fake range anxiety, but traded due to annoying misfires)