How dynamic? Resources can be updated to point to new immutable objects. For instance, as an operator of a website, I can sign the resource `/comments/10189265.

How dynamic? Resources can be updated to point to new immutable objects. For instance, as an operator of a website, I can sign the resource `/comments/10189265.json` as referencing an object with a particular hash, and then when there are additional comments, change the object it references. How fast things like this can update are dependent on the implementation, which I haven't read.