Hidden tracking of changes might in some cases be a security issue, if one sends a document which contains tracked information not supposed to be available for recipient.
Possibly when opening a document with hidden change tracking, an infobar could be displayed, or a status bar icon (this still be mostly unnoticed imo), or some other way of informing user about the mode (and how to proceed)?
Makes sense. Moving to NEW
The fix for Bug 83958 solves this problem on the following way:
If there is at least one hidden tracked change in the opened document,
Writer enables the Tracked Changes toolbar automatically with the icons of managing the changes.
This doesn't depend on the state of recording changes (but if recording is enabled in the document, Writer always switches on the Tracked Changes toolbar, i.e. without hidden changes, too).