If the taunt itself is concidered both a buff and a positive status effect (buffs being a subset of positive status effects) and the TM granting effect is concidered a positive status effect (but not a buff) then it makes perfect sense that StHan doesn't gain the taunt but still grants TM if he's affected by buff immunity, while QGJ can still dispel both effects (taunt as well as TM granting). In that case everything works according to the wording of the skill descriptions.
The bug list mentions StHan's 'draw fire' while he's affected by shock. I'm not sure what exactly it refers to.