How to highlight changes when comparing versions of a document in OS X?

I've been exploring the versions functionality of the new document model in Mac OS X 10.8. It's mostly similar to what was in Lion. In the title bar of a supported document choose "Browse all versions…" from the drop-down menu.

It seems handy enough, but how can you easily tell what has changed between each document without having to manually scan each line? I assumed there must be a feature to highlight the changes but I can't find it. Has anyone figured this out?

Sadly, I'm quite sure the highlighting doesn't exist. Apple's documentation doesn't mention it either: OS X Lion: About Auto Save and Versions (I know it's from Lion)

Mountain Lion changes to Auto Save doesn't mention it either. What's New in OS X v10.8 (Auto Save is mentioned under AppKit)