If you know whose car it is, it would be an asshole move to call parking authority. But if it’s some rando, don’t feel bad about calling. For me, 90% of the time it’s someone connected to the restaurant next door and I just walk over and ask them to move it. But if I don’t recognize the car and no one there knows whose it is, I have called. I’m pretty reluctant to call the cops in general but in this case they’re just ticketing the empty car — you’re not inviting the danger of a violent confrontation.