[Joseph Jostar]

The 'bare fists' sub-weapon from Mixed Martial Arts isn't being used to Riposte when Ambidexterity is toggled ON, regardless of whether your hand slot is empty or equipped with an item. Tested it with Ambidexterity OFF too, just to be sure, same results. That is to say, the Riposte was with my main-hand weapon instead.

(Yes, I have sub-attack.)

[Neus]

This isn't a bug, and I'm not sure why you think it would be one.