Well OK but sometimes a script could be running for years, during which any change to a file will result in bash executing random bytes...
Imagine if you press down on the mouse button meanwhile someone moves the screen up or down... you end up pressing on a different person's face. So I don't see any case where allowing this adds any value to bash. In fact I don't recall any other program with such scary behavior. I mean it's fine with me if bash will execute my script version 1, or my script version 2, but not some mishmosh of random bytes. Surely a little itty bitty check can't slow things that much down. So if I were bash I would bail out "$0 changed on disk. Bailing out rather than executing random bytes."
