I'm a TOEFL iBT Speaking Rater and I would have to disagree with the hedge words you suggest in the beginning of thia article (for example, "That's an interesting queston. I've never thought about that before."). In my four and a half years of scoring, I've literally never heard a test-taker respond this way. That would be an appropriate way to buy a little time on the IELTS speaking test, but for TOEFL it would definitely lower a test-taker's score. You only have 45 to 60 seconds to respond to a particular prompt. Wasting time with these kinds of phrases would be judged very harshly by raters who are expecting to the speaker to expand on a topic in a very limited amount of time.