Melee hit targeting inaccuracies
Compared to vanilla Morrowind, OpenMW seems to detect melee hits inaccurately. Whereas OpenMW attempts to directly evaluate an attack's angle in two planes using relevant GMST values as degrees of tolerance (fCombatAngleXY & fCombatAngleZ), Morrowind.exe seems to use the sines of the attack's angles multiplied by 90 when comparing with those GMSTs. This results in OpenMW allowing attacks to hit at wider angles on the XY plane. As for the Z component, OpenMW is even more inaccurate:
2024-03-22_10-10-26 2024-03-22_10-13-28
It seems that Morrowind.exe considers the entire height of the target's bounding box when checking if an attack's ZY angle is within the allowed range, but I'm not entirely sure.
I did a bit of tinkering with GMSTs to try and determine how Morrowind.exe calculates valid attack angles; here is a diagram with my findings: