I create a selection (rectangle or ellipse) with a feathered edge. I apply something and see that the selection size was incorrect. I undo the changes, select again the selection tool and click my existing selection. It should remain the same but whom me the rectangles at the corners allowing me to resize my selection. But it will grow accidentally. The marching ants don't stay at 50% opacity.
Well, it is enough to stay in selection mode and click inside the selection. It grows.