I meant that the old tree and the new tree both originate from the same source (i.e., your code), and if both were annotated with some kind of hashes of their contents, you wouldn't need any diffing to find the changes. You could simply compare the annotations on corresponding pairs of nodes and if they're the same, you don't need to descend any further and compare their contents - you already know than anything below that node is going to be identical.

Also, have you compared the performance of whatever you're doing with a simple PJAX-like approach? Considering that browsers are very good at parsing HTML, I wonder how fast that would be compared to doing quite a lot of DOM calls, which you seem to be doing (?). I'd definitely be interested in that comparison.