I will adapt the documentation first.

The file would also have to be moved from Interaction to Controller folder. Maybe there are other files that share the same problem...

Within Code/Interactions DisplayInteractor is the only class being derived from OperationActor only. All other classes here are StateMachines or classes bein used to build up a state machine.

adding wiki specification page for core change request

By the way, does anyone know the status of QtFreeRenderer? Is there a test for it?
It references mitkDisplayInteractor and mitkDisplayVectorInteractor (a real state machine).

DisplayVectorInteractor uses DisplayInteractor as OperationActor to send actions to. DisplayInteractor is given via constructor to DisplayVectorInteractor.
OperationActor is located in folder IO. DisplayInteractor will not be perfectly located there as well. So one can stand leaving it in Interaction folder.
Still its name is misleading. DisplayActor would be better, since actions are converted to changes in renderer here. This would also show usage and help to divide function of DisplayVectorInteractor and DisplayInteracor. DisplayCVectorInteractor then could also be renamed to DisplayInteractor, because the additional "vector" doesn't have any meening!

as there also is a mitkDisplayVectorInteractorScroll and a mitkDisplayVectorInteractorLevelWindow, renaming of all classes could be less worth the work.

ready for commit if core modification flag is granted

Removing old flag

The DisplayInteractor has been re-worked and is now implemented as a EventObserver using a statemachine.

So, the proper name would now be sth. like DisplayInteraction or DisplayInteractionObserver.