Updated Edge and it now seems to put a frame with rounded corners around every website
Edit: Looks like you can opt-out of that "new look and feel" pretty easily under the appearance settings but still, whats with putting rounded corners everywhere?
Edge is copying a lot of stuff from the yet-to-be-released-on-Windows arc browser. This is one of them. They seem to have not added the other stuff that interfaces with it like the one window split screen.