Scratch

I've heard that the Scratch API that lets usernames be validated and their Scratch information to be found doesn't work if the user has special characters in their username or password, but a user called Squawkers13 has complained that the block library website won't let him log in (it uses the username and password confirming API to check) and my updating images and links in posts won't link to any of his information as it should.

Does anyone know what is causing the problem?