I do not in any of my testing see anything getting removed nor is there any code in our files to delete them unless you physically check the delete function
I did a test on my site and added a field called testing children to both a cat additonal field and a review extra field and applied it to the children
This is the result so as you can see it works that I am seeing here
http://www.reeftalk.com/reviews/show...p/product/1865
I would need more info like urls etc to try on your site but this is clearly functioning in my testing of it