Why is such an assertion "damning?" It seems to me you are taking one small aspect of science, namely falsifiability, and stretching it is if it applies to the general principles under which any sentient being would undertake to understand the universe. An assertion just as "damning" is saying "that's how evolution did it." Truth is, neither assertion is particularly "damning." They just happen to be different ways of looking at the universe, and they both work quite well. They can even be combined.
Fester, don't you see how important this is? How can you test some idea, if the idea cannot fail any test? If an idea can't be tested, how can it be considered scientific? It would say nothnig about the way the world is - it couldn't predict anything.
An assertion just as "damning" is saying "that's how evolution did it."
The point is, there are possible observations that would say "evolution can't have done this". You've seen the list: the Precambrian rabbit, the mutations that are shared the wrong way among people, chimps and gorillas, and so on and on.
But there are no observations that would say "the designer couldn't have done this." ID is inherently untestabale.
Merry Christmas!