Why do Chasidim button their double-breasted Shabbos coats right-over-left, which is the way most women’s coats and blouses are buttoned? Did it start with, maybe, a left-handed rebbe?
No, it has to do with the idea that the right side which represents chesed should always be on top of the left side that represents din. There are shirts that button the same way as well. I’m pretty sure Litvish frocks do too.
Modern clothing is based on being right handed. It’s easier to button for men with left over right. For women, it was assumed the some one else, still a righty, would button them up.
apushatayid, it actually the reverse. The reason the buttons are on the left and not the right side is because non-Jewish royalty practices. The men dressed themselves, and the women had other women dress them. So the one doing the dressing would always have the buttons in their right hand and space for the button in their left hand. That’s why non-Jews, and secular Jews, find the button on hassidic men’s clothing puzzling.