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Why not use boons (see: HELP BOONS) to reward people for catalyzing roleplay (creating/running events, leading sermons/discussions, or consistently playing in-character in a way that positively impacts others' experience). There are countless ways to reward people that don't involve combat that could be easily handed out somewhat regularly. Some easy examples range from experience bonuses, gold drop bonuses, an extra minor trait (for the duration of the boon), a flat experience reward, a small NPC damage shield (3% or something). All of the boons could also, obviously, be proportional to the event.
Now I know that good old-fashioned in-character fun is its own reward, but positive incentives never hurt anyone, especially incentives that don't actually cost anyone anything. Even if the boons are relatively tiny, I think the psychology of knowing that good-behavior is rewarded would dramatically increase peoples' likelihood to play in-character.
Just a thought! Feel free to tear it apart.
"Our lives are not our own. We are bound to others, past and present. And by each crime and every kindness, we birth our future."