In theory it works something like this: For every piece of clothing the clauses are executed one after the other and the one with the highest factor is likliest to be picked. You know, in a factor x divided by the sum of all factors given out certainty. The exception is that if the engine encounters 100+ for some piece of clothing it'll use that.
Imperial crown/Chaliph turban / 0 is given out to every person (factor 100!) that the modifiers do not apply to (100 * 0 = 0). So everyone that is an emperor or who's wife is an empress, who is feudal and who is not peasent leader and heresiach will get it.
Putting this into 0 would disable the imperial crown for celtic people:
Code:
modifier = {
factor = 0
OR = {
culture_group = celtic
}
}
You'd then have to make sure that the guy is eligible for the kingly crown instead.