[TheIronGolem]

hero.child[sk(Skill)].field[BonComp].value += field[abValue].value

This is why it's stacking. You have multiple scripts pointing to the same skill and saying "increase the competence bonus by X". Instead, try this:

hero.child[sk(Skill)].field[BonComp].value = maximum(hero.child[sk(Skill)].field[BonComp].value ,field[abValue].value)

Or this macro which amounts to the same thing:

#applybonus[BonComp,hero.child[sk(Skill),field[abValue].value]

This means "set the competence bonus to X or the existing bonus, whichever is larger".