You clearly know more about this than me, because I'm currently Googling to understand what "diametrical corners" are. But in a simple implementation, wouldn't the x and y velocities both be reversed at once with a corner hit, both side and top/bottom collisions having been detected "at once" in the same part of the code between updating positions? And then the logo would just bounce out exactly the way it came in?
In fact I don't see how it ever could hit a a corner exactly.