The original thread was started by Neil deGrasse Tyson saying that Maverick would be "splattered" during ejection at mach 10. Scott Kelly responds saying he went on a space walk from the ISS at mach 25. The gardener is technically right that mach numbers don't really apply in a near vacuum. It's also kind of off topic because we know the Darkstar is in the atmosphere and not in space, and therefore there is no "re-entry". But Scott is right that the real issue would be heat and not getting splattered.
I also want to point out that we don't actually see Maverick eject, and it's likely that he would have been ejected in a capsule (like in several real aircraft like the B-58) rather than just thrown out of the plane in his pressure suit as Scott suggests.
Yes, but the gardener guy is specifically talking about the ISS flying in a vacuum. So he is not wrong. I find the comment of that Bruno dude just condescending.
I would hypothesize that the indicator for mach and air speed are decoupled from each other, as a true mach reading would likely give an indication of how hard a plane is working to push itself through the air.