If you use Explorer to copy a file, and then press Ctrl+Z to undo the copy, and you had file deletion confirmation enabled, then Windows 7 would display a confirmation dialog to verify that you really want to delete the file. But Windows 8 no longer shows that confirmation dialog. A customer wanted to know why.
Overwhelming customer feedback indicated that even though it technically meant deleting a file, the confirmation dialog when undoing a copy was unnecessary. Undo operations in most programs do not prompt in general, not even if the Undo is potentially destructive (such as undoing a Paste operation). All you're doing in this case is deleting a copy of a file; the original is still there, so there's no data loss. And if you forgot where the original was, you can get the copy back by Redoing the operation.