Well, placing papers on cars is legal in most cities, and is not littering unless the recipient (or weather) places it on the ground after it's been placed on the car.
All one has to do is discard it. To go the extra mile to trudge down to the police station or Mayor's office and make a stink about it appearing to be a ticket would indeed make the person a vindictive jerk.
Now, as an aside, the mindset of one who sees a "ticket" on their car from a distance is probably not conducive to a positive response to the pitch.
The fact that the poster here clearly calculated the weight of his actions versus the impact of the preceding event the on the attendee was what I thought was interesting.
It's a calculated risk, and one or two pings of interest is clearly worth the possible fine.
I don't know that 'impersonating' would really be a good description here. The rest of the 'ticket' makes things pretty clear that it is not an official communique of the city's.
