Contrary to what you and others say, the infiltrator is unquestionably presented as a ninja-class. Infiltrators hunt bounties. Infiltrators assassinate militia. Infiltrators break into tax offices and steal money. I can't think of any aspect of the infiltrator that is not ninja-like. It is therefore consistent to expect the infiltrator to also assassinate nobles; not merely stab them in the leg to keep them in bed for a few days (by the way, how is that not 'ninja'-like too?).
ninja?... I thought they would be more like 'Robin Hood's.
... or as the 'El Zorro': Honourable noble at day, infiltrator at night.
mmm... maybe, when unit-less they could move as adventurers... This would make them a bit less evident!
