Calligra/Libs/KoText/Change tracking
Change tracking in KWord refers to the ODF specified change tracking. It is limited to monitoring editing actions and saving within the document the information about the author, the time stamp of a change (eventually with a comment). It is later possible to accept or reject individual changes. It is not a version control system. Further, it is not a system meant to send "diff" to somebody else so he can "update" his document.
The use case of change tracking is the following: User A creates a document. He/she passes this document to User B for review. User B edits the document with change tracking enabled. All his/her changes are saved "flagged". User B passes the document to User C,... Eventually the document goes back to User A. It now contains all the modifications done by the different reviewers. All these modifications are "flagged" with their author data, date, eventually a comment. User A can for each of them, either accept the change (in which case the change is "merged in") or reject it (in which case the change is discarded).