100% for. A physical frame will have a white mount, same idea

For, because who gives a shit. It’s just pixels.

I use white border because I cross cameras in different aspect ratio and they all ended up nicely centered if there is white border. Plus it feels more like gallery viewing in museums. What I against is people put their huge logo or signature on their work. No one is going to steal social media share size of image. There is no point for that other than self ego.