I personally would broaden the request to highlight all local overrides. Like you, my most frequent use of it would be to deal with text reflow.
When I finally upgraded from InDesign CS 5.5 to CC a couple years ago, the one new feature that I was really excited about was the ability to highlight overrides. I use it a lot, and now that I just got it relatively recently, I am sad to "lose" it again when I move over to Publisher.
I hope something similar eventually makes it into Publisher. In fact, Publisher could really take it to the next level by providing a highlighting interface where you could customize what is highlighted, whether all highlights, or a selection among things like tracking changes, leading changes, no break, etc.. And then the next level of awesomeness would be to allow the user to save different presets of highlighting settings. As for as UX, I think the current snapping manager interface (which is a superb implementation in my opinion) would serve as a good model. Just as you can turn snapping on and off with a single click, yet you can manually change settings or select presents, I think you could do the same kind of interface with a "highlight manager."
To me, that would be a killer feature that would set Publisher apart, and I would use something like that a lot, but I wonder how many others would find it helpful. Of course, even if it had wide appeal, I understand it would have to be a later addition after more essentials are nailed down. But perhaps Serif could keep it in mind.
