A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 21 March 2013
If I target and bow a Paragon with Kuon's Legacy and the player reacts with Iron Will, will the previous effects be negated as well i.e. straighten and +3F?
Iron Will Reaction: After another player targets your Paragon with a Battle action performed by a Personality with lower Personal Honor: The action's costs are ignored and its effects are negated. That player may take an additional Battle action.
Kuon's Legacy Battle/Open: Choose your performing Personality with 7 or more base Force: His eyes go dead. Straighten him. Give him +3F. He may not perform actions. You may target and bow a card at his location.
Alex Jones (rules official), 21 March 2013
If I target and bow a Paragon with Kuon's Legacy and the player reacts with Iron Will, will the previous effects be negated as well i.e. straighten and +3F?
Iron Will Reaction: After another player targets your Paragon with a Battle action performed by a Personality with lower Personal Honor: The action's costs are ignored and its effects are negated. That player may take an additional Battle action.
Kuon's Legacy Battle/Open: Choose your performing Personality with 7 or more base Force: His eyes go dead. Straighten him. Give him +3F. He may not perform actions. You may target and bow a card at his location.
If an action's effects are negated after it has already created some effects, existing ongoing effects are negated but prior instantaneous effects are not undone.
See Duration and scope of prevention effects: Continuous and ongoing effects that came into being before a relevant prevention effect was applied are still affected by it, by default. Continuous and ongoing effects that came into being after a relevant prevention effect was applied are also affected by it while the prevention lasts, by default. Prevention of instantaneous occurrences is never retroactive. Specifically, if “all effects” of an action or trait are prevented partway through the action or trait’s resolution, instantaneous effects that have already resolved are not undone.