违心配角
[wéi xīn pèi jiăo]
In English, it's 'Reluctant Supporting Role'. One may consider him/herself not a main player on stage but an unimportant or insignificant supporting role and feels reluctant to accept reality. Therefore, the netizen probably expresses modest, self-mockery, humble or inferiority complex by choosing this username, depending on how serious he /she is.