I know there's a difference, but I don't know if it won't get confusing for users. I'm not sure if it's made clear enough when a diff is reverted or not. If a user sees a reverted diff between 6 and 5 for example and then if he goes on to diff 6 to 7 it may be weird since he could see what would look to him as deleted content.

Our users are smarter than we assume, they can figure it out :) We can add a "swap" button on the diff pages to make the distinction more clear.