The thread you are referring to begins 12-12-2014 & has the last post in 08-31-2015. lt's been many patch-fixes since then & the problem is fixed....otherwise the topic would still be alive!
I can't replicate the negative AoA scenario under any conditions at all.
From 20m & above at supersonic speeds, my AoA is always positive.
In the pictures I'm flying at ISA, RA 60m, M1.12, AoA +1°, Flight Path ang. 0.0°.