Thanks everybody. I guess my cars are so old --- early 70's & 90's -- that they don't have this new fancy fuel venting eqpt to worry about. My 70's Ford truck just has a canister which captures the extra vapors, and vents with a hose to the air cleaner, where the vapors get sucked into the air intake when the engine is running. I had to replace the hose from the canister to the air cleaner last year, otherwise I'd not even know it was there. My 90's Corolla, I think it is configured the same way, just a canister which vents somehow to the intake manifold. But I could be wrong about that. It might vent back into the gas tank on that car.
No worries. I don't overfill the tank anyway. Not enough money! I'm lucky to get it to half full. lol ..
But thanks for your illuminating comments, I can now see that indeed with newer cars at least there's considerable damage that can be done by overfilling, and since there's so little to gain by overfilling, why risk having to take the time and pay the dollars for repairs when the diagnosis is often time consuming and the repairs expensive, and it can all easily be prevented by stopping fueling at the first click. Good advice!