Dividing by 1023 or 1024? The final verdict on analogRead

Please, can someone put this thread out of its misery?
Oh, the humanity!

Let say we have just 1 bit ADC, 0 or 5V. Just two possible values. Should be /0 used?

No, because 21 is 2, so by GoForSmoke's logic, we would divide by 1.