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 December 2007
For the sake of the argument I am NOT a crab clan player.
I have a Hida Yaheiko in battle and she is being destroyed and I play Courage in Death on her. (Reaction: Before one of your Personalities is destroyed during battle: Give another target Personality a Force bonus equal to your Personality's Chi. If you are a Crab Clan player, delay your Personality's destruction until after the battle ends.)
Would then taking Yaheiko's Reaction: Before a card effect would destroy Yaheiko: Negate the destruction. Cause Courage in Death to fail?
Zen Faulkes (rules official), 21 December 2007
I have a Hida Yaheiko in battle and she is being destroyed and I play Courage in Death on her. Would then taking Yaheiko's Reaction cause Courage in Death to fail?
You couldn't use Yaheiko's Reaction then, because Yaheiko is not being destroyed due to the effect of Courage in Death.
A player, 21 December 2007
RE: This.
I believe the above answer is flawed (not to fault the answerer entirely; the question, I also believe, contains some ambiguity).
If I may put forth my take on it:
It is asked if a non-Crab player using Courage in Death on Hida Yaheiko, then using her Reaction, would cause Courage in Death to fail due to negating its cost (I surmise from the thread title, though the question doesn't reiterate this notion) with the second Reaction.
Firstly, the notion that Courage in Death has a cost should be corrected. The contraints block of that action contains no costs, only the Reaction Trigger (see here, under Contraints Block). Second, since Courage in Death is taken as the first Reaction, its effects have already resolved when Yaheiko saves herself. Taking away the trigger of a Reaction that has already been taken with a further Reaction won't retroactively negate its effects. If Yaheiko's were the FIRST Reaction used, however, negating her destruction before Courage in Death, that would leave Courage in Death with nothing to react TO. Lastly, the linked answer misses all of this in assuming that the asker thought that Courage in Death was causing Yaheiko's destruction, but I don't think that was the case at all.
Thank you for your time, and I hope I've helped clarify things.