Have people's social rating be an indicator of how NPCs should treat them.
So the idea here is that if there were a social toxicity prevention mechanic similar to that of Overwatch's voting system, where every day you can rate your interactions with people, and your vote is limited to a few people to the match, the very edge cases where someone was very cool, or very negative would stand out, and those people would begin to climb the social rating ladder or fall down and be negatively scored.
There are probably flaws in how the concept would carry over from overwatch to say an MMO, but it would effectively make your personal interactions with people, and your overall social perception a perceivable part of the world through the NPCs and anchor you into being either nice neutral or negative.
It could totally be gamed, but in aggregate you would find that how you treated people in the game would also trickle down into how NPCs feel about you. Maybe doing a couple quests would improve this attitude or maybe it would take a lot of quests in the entire node to shift this attitude etc.