It would be great if there was some kind of undo-functionality or even an overall confirmation dialog when moving pages per drag&drop in page tree-view.

Currently it is very "easy" to drag a page and drop it accidentally into the wrong location, for instance because a user is unaware of the drag&drop functionality when clicking at pagetree-entries or when someone does not know how to cancel a drag-operation. It seems to be that currently there is no easy and obvious way of undoing the operation.
It gets even more problematic when the user does not remember/know the former location of the accidentally moved page.

Generally, this kind of no-confirmation-just-do-it UI-experience seems to be somewhat unnatural in confluence, because other operations with similar impact do require a confirmation.