谁人幼稚成性谁人孤独成癖
[shéi rén yòu zhì chéng xìng shéi rén gū dú chéng pĭ]
This username translates to 'Who has an immature nature, who is addicted to loneliness'. It expresses a person's self-awareness or critique of someone (possibly themselves) being childish and prone to solitude as a habit or preference.