As for the Immortal and modesty thing I think he is right, but he is generalising, for example, salah is obligatory, but if one does it to show off, then it can have the opposite effect! Similarly hijab is obligatory, but if someone wears it to show off that they are supposedly modest they it may be wrong?
But the whole point is that this is not the general reason, it is not the religious reason, noone should wear hijab to SHOW OFF their modesty, they may wear it to show that they try to be modest, or they wear it because they believe God has told them to.