Travis Scott, when a woman stabs someone in SotI she’s probably Tempting Fate as described, yeah. But how you frame that is up to the MC. It doesn’t have to be “she murders them / she somehow fails”. It could be “she’s not discovered / everybody finds out” (with the assumption that the person will die regardless), or it could be “she doesn’t become accursed in the eyes of Odin / she totally does” (with the assumption that the assassination attempt will guaranteed fail).
The way I’m reading most PbtA games is that players making Moves while adhering to the prescribed trigger and move outcome grants them full system-supported agency, while anytime players try to do something in the fiction that falls outside of those moves, the MC decides the outcome based on what makes sense from a simulationist and/or dramatic perspective. A woman stabbing someone in SotI is undefined – there is no move for it for a reason, so what transpires is decided by the MC by fiat. Is this an open fight between a knife-wielding woman and an armored, axe-wielding man? The woman stands no chance of inflicting grave harm by tempting fate, but might be able to question his honour or otherwise destabilize him. Is she stabbing him in his sleep? He will definitely sustain grave harm, maybe just perish outright – the stakes are about something else.
In my view that is why SotI is so elegant – it prevents players from seizing agency in ways that don’t conform to the cultural setting, which forces them to further their motives in ways that are thematic to their characters. Which in some ways include rebelling against and transforming that same cultural setting.