but what if client had a crappy old browser but you rendered with modern browser, which will be rendered differently. Wouldn't be better if feedback contained computed HTML doms and you could render yourself with a given client?
The really crappy old browsers won't see the feedback button. We do store and show HTML doms, which helps to debug if necessary, but most of our users collect feedback on such a large scale that it would be too time consuming to offer a manual solution like this.