I cannot imagine a single situation where this would be an issue. Nor do I remember a single good rpg where first-person dialogues are harmful for immersion.
Maybe, some Medieval simulator in Japanese where you should use different words for "I"

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You just choose the lines which fit your character best. That is the same for 1p and 3p.
I don't think you understand at all.
The Origins are distinct characters with distinct backstories and distinct quests. Villainous drug-addicted Ifan has a different personality than haughty, smugly superior Red Prince, who has a different personality than cheerful, loopy Lhose.
If each of those characters used the exact same dialogue, that defeats the point of giving them distinction and history and personality.