Despite having a mild and friendly personality, Po also developed a severe self-loathing, believing himself a failure for being both obese (but in reality he is a healthy weight for his species) and a species not known for a warrior tradition. When he gets upset, he usually gorged on food to dull the pain.
He does seem perfectly capable of having manners though.
Po's personality can perhaps be compared to that of a fan of Kung Fu movies. He is generally friendly, lovable, passionate, a bit impulsive and good-natured, but sometimes comes off as chummy and informal, and his enthusiasm and excitable demeanor occasionally cause people to misunderstand him,