Have to disagree with you there - this isn't even just about simplicity, it's about clear thinking; even experienced users will learn to associate one bar with moving around the cursor and another with doing stuff to the selected text. Plus, purely in terms of ergonomics, if you're tapping along on the bottom bar to navigate you aren't going to want to move all the way to the tap bar to collapse the selection to one character; easier at that point just to drag the selection handle, or tap on the |<- button more than once.