I was trying out data-permanent and was confused for a while because it seemed not to work. Then I tried moving it to an ancestor element and it did work.

Repro

• Start with <div id='myelem' data-permanent></div>
• Use JS to mutate it in some way (e.g., document.getElementById('myelem').classList.toggle('expand'))
• Perform an enhanced nav that returns equivalent content (i.e., <div id='myelem' data-permanent></div>)

Expected: The expand class should be retained
Actual: It is not

However if you replace the markup with <div data-permanent><div id='myelem'></div></div> then the class is retained

I guess diffing only uses data-permanent to decide whether to recurse into the element, but I think it should also use it to decide whether to synchronize the attributes on that element.