This one struck me as something that elicits a bad knee-jerk reaction despite there being a good reason for it. I seem to vaguely recall something regarding moving vs copying related to file system atomicity, but can't remember the details right now.
Yes. The move rename operation is atomic in any reasonable file system. With the default behavior Emacs can always keep the previously known good data in place even under power failure, disk failures, etc. if the new file is corrupt you go back to the exact old data (no bits moved in the disk.)
