I've been looking at Bolin's position in the infobox, and it says officer. This seems a little stiff to me. Let's face it: He's only twenty, uneducated, and while a talented earthbender, he's no sophiticated metalbender, but can uses the brute force of lavabending.
The insignia on his arm doesn't translate directly into a rank of the US military, but it is very close to the insignia of corporal. This is the symbol used by, among others, the UK and Dutch military. (And in neither corporal is considered an officer.)
What do you think? Should tis be changed?