its only about programmatic semantics. most everything handles the space character ' ' or " " different from other symbols like 'a' or 'dds'.
the blank space character gets lumped into other strange characters such as new lines - '\n' or blank characters - ''
It is also not unique, as some special characters on certain computer environments don't have a representation, and get parsed to a blank character ' '
In some computer environments where we were passing files back and forth from MAc to Windows to Linux, we sometimes ended up with (' ' == ' ') to produce a FALSE result (the double equals sign simply signifies a comparison operator). It was false because there were hidden symbols existing in the space that we couldn't see due to computer cultures being different across our team.
I am unsure whether or not this problem would ever occur when talking stictly passwords, but having no spaces in special areas such as passwords and function names and file names is defiantly the better way to go always. Parsing spaces in filenames is a whole different story, with some programs adding a % to a space to remove the space so you would have the name being the%name
NIST 800-63B, it is note that space should be accepted in password, see pages.nist.gov/800-63-3/… Guess not everybody listen to them lol