Here is the text of the NIST sp800-63b Digital Identity Guidelines.
Very common for pass phrases, and not dissuaded. Pass phrases are good for people to remember without using poor storage practices (post it notes, txt file, etc) and are strong enough to keep secure against brute force attacks or just guessing based off knowledge of the user.
On one hand, that’s true. On the other hand, a person should only need exactly one passphrase, which is the one used to unlock their password manager. Every other password should be randomly-generated and would only contain space characters by chance.
gosh who would want an uncommon character that obviously most average people aren’t thinking about in their passwords, that sounds like it might even be somewhat secure.
I’m with you, despite seeing lemmings downvote the heck out of your comment 😢
The reason, and specifically for whitespace at the beginning or end of a password, is that a lot of users copy-paste their passwords into the form, and for various reasons, whitespace can get pasted in, causing an invalid match. No bueno.
Source: I’m a web developer who has seen this enough times that we had to implement a whitespace-trim validation for both setting & entering passwords.