世界那么大装无知给谁看世界那么大装无辜给谁看
[shì jiè nèi me dà zhuāng wú zhī jĭ shéi kàn shì jiè nèi me dà zhuāng wú gū jĭ shéi kàn]
It means 'in the wide world, who are you fooling by pretending to be innocent?' which implies that there is no need to pretend in the vast world because your pretense of ignorance will not be believed by anyone. It's quite long for a username though, maybe it's better suited for a signature or personal motto.