Not quite. I'm saying there are 256 discrete numbers (0-255) and 255 intervals between those numbers. Most of the real values will fall into the intervals and get mapped to 0-255 somehow, maybe by nearest neighbor, but I'm not trying to define how they get mapped. The point is that 255 is the largest number that can be represented with 8 bits, so you should normalize by 255.
I wrote a longer replay to alterom but it looks buried for some reason.
https://news.ycombinator.com/item?id=48365800