Original objects are never modified, but transparently wrapped by observable proxies.

Proxy = observable(object) Creates and returns a proxied observable object, which behaves just like the originally passed object. The original object is not modified.

I saw object proxies being the solution to doing diffing so that this approach could compete in any scenario that a VDOM could

Here's a proxy store I wrote to derive the value of a store nested within other stores, it plays nice with typescript and can go infinitely deep