Why isn't Mello mellow?

I don't know. Why is Light so dark? Why isn't L（デスノート） a loser? Why is Near so distant minded?

it does say in how to read 13 that near was meant to be called mello. so maybe if they had kept that then mello would be the mellow one...

-is that confusing? it confused me-

Well, why would Near be Near? He is quite far from humanity and the outside world, isn't he? He is far from able to accomplish anything without the help of others, または even take care of himself, for that matter.

Mello is loud, impulsive, and aggressive, so I do see your point there. I think that they both chose those aliases that contradicted them on purpose.

I actually think that Mello's emotions make him can go both ways. On one side, he is very well-spoken, intelligent, and insightful, but his inferiority complex leads him to do reckless, selfish, and infantile things, as well as loose sight of what is truly important, and even end up killing others (sadly). In the end, he did know what was the right thing to to, though.