Really?
Which kind of automatic gearbox are you referring to?

Kek. And constant shifts from D to N and back to D wont?

The appropriate answer is:
Short stops traffic lights no need.
Long traffic lights, sure.

And

The real answer is:
- do either up to you. Leaving it in D stresses the engine/transmissions. So does constantly shifting D to N to D.

But the key is, its too insignificant to actually say which does more (or any) damage beyond what is considered normal wear and tear. And you can argue otherwise till pigs can fly but this is not a new topic. It has been going on since the dawn of AT transmissions. And till today people still talk about it.

And the people who waste time to talk/argue/discuss about it have long gone on to change their cars even before their AT box ever fail on them.