You also have a similar problem when you render opaque, rectangular images without the clamp edge mode, and the renderer is in tiling mode, so the borders wrap around when your picture is halfway between pixels and become a mix between the top/bottom or left/right colour, corrupting the edges. Easy to fix, but annoying until you get what it is that corrupts your edges.
Also: "The original color can still be retrieved easily: dividing by alpha will reverse the transformation."
C'mon, you can't say that and then make an example with alpha=0. Do you want me to divide by zero? The ability to store values in completely transparent pixels is lost.
It would be more accurate to say that the original color can be approximated. The approximation quality goes down as the transparency goes up, until at zero it gets lost entirely.
You're right. I didn't want to mention precision because it's a whole other can of worms, but one worth knowing how to deal with. I was looking at it from a mathematician's point of view, using rational numbers.
Also: "The original color can still be retrieved easily: dividing by alpha will reverse the transformation."
C'mon, you can't say that and then make an example with alpha=0. Do you want me to divide by zero? The ability to store values in completely transparent pixels is lost.