We continue to suffer under one poor choice I (Ward) made early in the project: Drag Refactoring. This was a design goal. I had hoped that a carelessly organized set of pages could be drag and drop refactored into a better design.
Wait. Joshua has straightened this out. No need to end refactoring. github 
(2019)
See Footer Item Search for motivation.
I can't remember where I have done this in my own writing. (Except for just now.) I suspect it is too hard.
Copying a paragraph is made hard too since you have to remember to hold the shift key down while dragging and ignore the fact that it seems to have moved the item anyway (It hasn't, refresh to see that.)
Let's embrace footer item search as our best method of exploring provenance by getting rid of shift-drag and adopting this simple rule: drag within a page is move, between pages is copy.
Of course how drag is interpreted is determined by the origin server. We don't have to worry about changing all servers at once. The copy interpretation will be obvious if other behavior were expected because less would happen on the screen. The copied element would remain in the source, not something that happened visually.