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I got officially that Loki cards cannot effect other cards that had been effected by Loki cards. So you cannot remove loop cards etc.
Why limit players' options? Being able to remove loop cards can be a great use of a Loki card, and doesn't unbalance the game at all. Also, your "official" mandate would add unnecessary complexity, as then players would have to remember which cards were affected by Loki actions throughout the rest of the game.
Better to leave well enough alone here - if the rules don't say an action is prohibited, then it should be permissible.