I think you should wear short sleeves and not give a **** what people say your parent can't force you to wear long sleeves no matter what they tell you. Your right its probably more about them than you about wearing short sleeves. But I also understand why you listen to them to keep the peace and not rock the boat. I have a good amount of scars too and you listen to that inner voice tells you to rock short sleeves. If someone ever asks just make up some crazy reason for your scars like "You never want to interrupt grandma while she is knitting." Be your self and show your arms of or not if you don't thats okay too. All I am saying is do what feels right to you and not to worry about what your parents tell you. Stay strong.