When we had originally designed the ModifierInterface, we believed that we would go through a prepare phase that would need to decide about in-placeness.

Subsequently, we changed to a different model for in-place, where the mutable Document tracks the in-place status for itself.

In light of this change, it is not clear whether the ExecInfo inPlace field is still relevant or necessary, or that the decisions operators are using to set it are correct, or what the consequences of setting it might be.

We should probably remove it, but we should at least look at all the instances and evaluate our options.