Bear in mind that bash is obviously restarting from the character position specifically but other shells might not handle this at all, meaning that they just us

Bear in mind that bash is obviously restarting from the character position specifically but other shells might not handle this at all, meaning that they just use buffered stdin. For such a small script the whole thing has been read into the buffer but a longer script might fault at an otherwise unobvious point. Unless you know that it is explicitly safe (ie the whole file has been cached before it starts) then you should really not modify any running file.