I don't know if this was discussed already, I've used the search button.
Entering and exiting cars to avoid death should be disallowed, it creates an unfair advantage just like c-bug.
Players with low ping like myself do not stand a chance against that kind of behavior since to us it looks like they're teleporting on top of the car and taking 100% of our armour in less than 3 seconds because of it.
tl;dr enter- / exiting cars should be disallowed since it is a bug just like 2-shots and c-bugging.