I enabled "Visual differences" in the "beta features" tab of my preferences on en-wiki. It did not seem to have any effect on anything.
Topic on Talk:VisualEditor/Diffs
You should see an extra button, towards the top corner of the regular diff.
Ah, thanks, I was looking for it in the "history" tab, as I was hoping it was the tool WMDeustchland developed a while back. I'd really prefer a Meld-like interface.