我知你长短我知你深浅
[wŏ zhī nĭ zhăng duăn wŏ zhī nĭ shēn qiăn]
In English, this translates to 'I know your ins and outs.' It conveys the idea of thoroughly understanding another person. Such a username reflects one who sees beyond superficial appearances, truly knows the strengths and weaknesses or true situation of someone (which may include oneself) and is able to perceive what cannot easily be seen on the surface. Here 'ins and outs' doesn't only refer to characteristics or habits, but even deeper into personal privacy or feelings.