You don't have to believe, just open your eyes and you can see it happen. I've seen plenty. I think the cases furtherest on that end are nodes that the author eventually finds "embarrassing" (or just gets sick of being voted down on) and demands that the node be deleted.

I'm not convinced that such nodes should be deleted (neither am I convinced that they never should be), but I've seen it happen many times. And I think a sensible deletion policy makes more sense than, for example, having the author replace the contents of the node with something completely different (or they just make it blank).