It's a wanted feature :).

I could see very good productivity here.  You could compare actions within an espace to see what the difference is (comparing patterns).  This would be really cool if you could compare an action that was copied from another and have some kind of history letting you know what it was copied from. 

Also, if differences between actions within an espace could be done, maybe refactoring could be done to refactor application code to combine.  (DIY principle)

I can even think of exposed webservice versions to check the differences. Overall, would definitely appreciate to have this feature.

Any updates on this idea? would be a great development improver.. Would also greatly help with comparing versions of actions (but also webblocks, themes, etc)

This should be a great feature.
I just want to add 1 more scenario that this feature can improve productivity: as OutSystems doesn't have built-in Branch feature like Git. I let my team members to use folder to isolate WIP version of actions, web-blocks, or screens... Once everything is settle, then we can merge / replace the old artifact (action/block/...) with new version. So, it would be good if Studio allow to compare code artifact. 
Best regards.