On that note I know that the manual for my Nolan specifically said to never do it. I would think this could also be looked at from the lawyer stand point. It sets up a grounds for defense if someone were to fall and have their neck snapped because the a chinguard in the up position caught something. It clearly states in the manual not to do it...
Can't remember the brands, but I did read a modular comparo a few months back that had a couple of them rated for riding chin bar up.. I believe HJC may have been one of them...... But you are correct about the Nolan. I have a Nolan and the manual says always ride with it down and locked. But on hot days at slow speeds I sometimes ignore the manual and ride chin bar up. My risk and my choice, and my fault if I end up face first in the side of an SUV.