In my testing all IE versions will have `document.readyState == "interactive"` almost from the top of the document. If a script at the top of the page does manage to detect the `loading` state then almost immediately there will be a `readystatechange` event. I could only detect this initial change when refreshing a page, but the `interactive` state is reliable. 

I believe `document.readyState == "complete"` is reliable and should be early enough for `<plaintext>` capturing because there are no resources to download and no page to be painted.