A family of Microsoft word processing software products for creating web, email, and print documents.
The only protection method that will allow Track Changes to work is the use of a content control. Even that, however, won't accomplish what you're asking.
From Word's point of view, there is no difference between "editing" a piece of text and "deleting" the same piece of text. Deletion is simple a particular kind of editing. The content control option "cannot be deleted" refers to the control itself, not to the control's contents.
If the "cannot be edited" option isn't selected, then the control's contents can be both changed and deleted. If the "cannot be edited" option is selected, then nothing in the control's contents can be changed at all.
At best, if someone completely deletes the control's contents (but not the control itself), then the placeholder text will reappear. You can change the default "Click here to enter text" to something more explicit by clicking the Design Mode button on the Developer tab.