While entering the archetypes, I've come across several instances of characters with Critical Strike, but no Favored Opponent feat. (In fact, I rarely encounter both on one character.) According to the Core 2e FAQ, a player can emulate FO using a Hero Point in order to use CS against any non-favored opponent who is also Immune to Critical Hits. Since this comes up relatively often, can we add a note in the Critical Strike description that describes this?