do not sure have copermine 1.2 this bug, waiting for 1.3 for upgrade my current system.
So:
Someone have album. Nature for example, and have photo called sky.jpg inside this album.
If he forget about this file and try to upload another photo with name sky.jpg, his never see any warning.His just get old picture resized to new size.
He can delete file correctly, rename it and upload again. But how he know what name he should use if he have now sky1 - sky10 and forget last number?