Sounds like you understand the "Pretty Voice" case.
For traits, the effects are never used until the traits are removed. Bandages, potions, spells, and a few other things all use the duration field within the effect for expiration. All actions, events, jobs, interactions, exploration, combat, end-of-day updates, and so on simply check the "traits" list. Generally it looks similar to this:
if person.traits.has("Mentor"):
Checking for a trait through the effects is tedious. Though most other effects don't have easy lists like traits so they use the tedious method.
Almost right on the MC spec, I said combat and sex, not exploration. During those events all persons are encapsulated by another class and put in the same list. So assassin, trapper, and nympho. Ranger would do something if it was included in the general awareness calculation. Geisha would do something if stress effected the MC. Bodyguard would work... if the spec actually did something during combat, but right now it's just stat bonuses. The description isn't technically wrong since doubling zero additional damage reduction is still zero, though perhaps misleading.
You are right about the tattoos.