An update on this, i've been toying with adding to dwarves and human :
[NATURAL_SKILL:DISCIPLINE:15]
Then i created a world, i made sure the [NATURAL_SKILL:DISCIPLINE:15] was also there in the save own raws of course.
Then creating a demigod dwarf in a dwarven hillock i went to a nearby human hamlet and killed dozen of humans one by one without anyone trying to fight back, their reactions, at least those not running away in panic were just the usual stupid comment "is that a weapon" or "death is all around us" .
I also noticed that when hit once, every target was trying to run away as if they had not discipline level 15 instead of fighting back their aggressor.
Hmm, i was wondering if it had to do with demigod and its insane stats/attributes screwing up the npc morale/reaction checks.
So i retired and created another dwarf in the same dwarven hillock, but this time instead of a demigod i created him as a weak peasant so the stats/attributes would be a lot much lower.
I then went to the human town , in another part of it to make sure the human there would not have seen the previous massacre in case it would influence their morale/reactions rolls.
Then i proceeded to kill dozen of humans again.
Very annoyingly, similarly to the previous test, no human ever tried to fight back, most of them were fleeing or making absurd comments, waiting to be killed in turn.
So it looks like discipline level 15 does nothing as npc still freak out as if they had 0 discipline. My peasant mace skill even went from his very low level up to Adept.
I then checked my character and he had a lot of "afraid of seeing X die" , so even for the dwarf the discipline level 15 does nothing, he was even afraid of a trauma that he never had too.
Same broken npc morale/reaction as df2014