This is another generic Qt and QtQuick problem, but in 5.8 we will have a different architecture for text-editing handles, so it should become possible to solve this nicely in the standard way: long-press to start selecting text, flick to flick the page. The present behavior is contrary to what the mockup shows: if you flick in a margin where no web content is present, it works, whereas if there is text, you will select text with your finger.