does he use the arm rests on chairs or he couch?

rest his arm on the desk while using the keyboard? or his arms on the chair while at the computer?

i can't imagine holding my arms up the whole time i am sitting.

yep..bad manners here sometimes too. i know i have put my arms on the table while eating.

also...the elbow is a sharp joint. bending presses from the inside. so inside friction.