My opponent targets my courtier with Shinjo's Courage. Before it resolves, I play Share the blame, dishonoring my courtier and losing 3 honor. Can I then seppukku, and kill my courtier thus removing the target of Shinjo's Courage, causing the Shinjo's Courage to fizzle/fail?
Share the blame and seppukku
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.
Reaction: Any number of times per turn, before you lose Honor from an action that targeted or was performed by one of your Courtier or Samurai Personalities: He commits seppuku. If the seppuku destroyed him, reduce the Honor loss to one.
Emphasis mine.
Share the Blame neither targets nor is performed by your Courtier, and thus is not a legal trigger for the Seppuku Rulebook Reaction.
Also, to show the value of searching the forum:
viewtopic.php?f=59&t=61532