We have a hard time telling when items in the backlog are changed. There is a change comment field but I can't make it required because the UI allows changes to be made in other views (e.g. table view). My recommendation is a)

When a simple value is changed, no need to have change comment - just log in history.
If any description/text is changed and change comment is required, popup diaglog or make it red/required depending upon the view they are in.