Quote- Why is world chess champion 丁立人 nicknamed 人哥?
人哥 could not be his nickname. It is how his fans wish to address him informally.
A nickname would be something like 超棋人, (Super Chessman), as his personal name, (for the Chinese, as you know, it is the last or third character), just happens to be 人.
The third character, 人, (and not the second or both characters), is chosen is because the third character is personal to him, as the second character 立 may be shared with his male siblings or first cousins, and thus not personal enough.
The question is why 哥?
Like all other cultures, the Chinese considers all peoples as part of the larger human family, like "All men are brothers" and "All women are sisters", that sort of thing.
So, calling him 人哥 gives his fans a sense of vicarious pride as though he is part of their own family, like a proud father saying a certain Olympic champion is his son or daughter. So, his fans or Chinese people in general are saying 丁立人 is one of their very own when they call him 人哥.
Even people who may be older than him would call him 人哥 because the word 哥 is also a form of extolment, (an expression of approval and commendation), because the Chinese extols age and the elderly which is equated with knowledge and wisdom.
However, this thing about age and the elderly may sometimes be used sarcastically or playfully like addressing a precocious child, 您老人家, like telling a young boy "You're the man"