>That said: doing this stunt in what looks like a suburban park strikes me as shockingly irresponsible. This thing can easily kill someone, wreck a vehicle or puncture a roof if control is lost...

What makes you think that someone who can:

1: Build this plane

2: Demonstrably fly it very well, with clearly a significant amount of experience in flying RC planes, and probably other high speed RC planes

will overlook all safety precautions and take what is likely the highest powered plane they've flown, where something is comparatively likely to go wrong vs traditional RC planes, and go fly it in their local park with people/houses/etc. around?