Because, then there can be multiple accounts that are variations of BigBird, and all annoying to differentiate for users. Such as Bigbird bigBird BigBIrd. Combi

Because, then there can be multiple accounts that are variations of BigBird, and all annoying to differentiate for users. Such as Bigbird bigBird BigBIrd. Combind with this, the fact that you have unicode characters, and it makes it very easy to 'spoof' as another user by simply changing the letter 'o', to a unicode circle, or various other tricks.