Originally Posted by angelorange
Did you mean that or the opposite?
Exactly that.
Modern turbofan powered transports have too high Mach No where mach effects have significant effect on stability and controllability (it is way above Macrit or Mmo) and too low power output at altitude to reach altitude where 1g stall and Mach buffet intersect. Valid when HTBJ was written. With higher bypass and improved aerodynamics, even more valid today. If you fly Airbus: altitude where Vls and Mmo meet is way below hypothetical coffin corner, which doesn't imply that it should be taken lightly.
Mach buffet is anything but stall. Depending on design one may experience pitch-down, pitch oscillation, trim reversal, roll reversal or many other unpleasant surprises but there's no rapid onset of drag and loss of lift that goes with pushing the aeroplane over AoAcrit.
When frames of reference are mentioned, here's another myth:
FBW Airbus in manual flight maintains 1G with stick neutral in pitch, therefore at higher FL, where gravity is weaker due to distance from the earth, it will pitch up to maintain 1G so constant nose down pressure is required to maintain level flight.
I am pretty certain that ensuing furious FCOM quotes and stories of "I've seen it" or "My friend has seen it!" will help me to somewhat explain origin and persistence of aviation myths.