> It should read:
> "administrative data structures that should be not shared 
> even between copies"

No. If they should NOT be shared, then making a deep copy is the correct thing to do. The problem with deepcopy is when you actually do want to share some deep data structures, but not others. Then making a copy is the wrong thing, since they will no longer be shared.

The current documentation is correct. I'm going to leave the issue Open for the time being, in case somebody can think of wording that is more clear and less likely to be misunderstood.