Level 45 deg AoB turns at M0.84 and FL410 were part of the IR profile on the mighty Vulcan over 30 years ago!
We also flew at FL 500+ and most definitely did 'prat about' doing fighter affiliation against F4s and Lightnings. The Vulcan had huge reserves of thrust and wing!
But the accident in the Pinnacle aircraft shows poor discipline, poor knowledge of jet aircraft performance limits, buffet boundaries, engine failure procedures.......
Leave the 'pratting about' to those trained for it - and fly airliners within the limits stated by the Aircraft Flight Manual. Assuming that an aircraft certificated to fly at FL410 will always be capable of reaching that height, irrespective of weight, shows unbelievably poor understanding of aircraft performance limitations.