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, 11 June 2007
If I am playing against someone who just brought out a card that is unique that I know I have a copy of in my deck. Can I use Dark Harmony to remove Unique so that I can bring my copy of that Unique card out?
Unexperienced versions have the same name and not unique, and you can have those out at the same time. It seems to me you should be able to have both out, as long as one says Unique, and the other does not. I understand I couldn't put two in my deck, because only one of a particular unique per deck.
Zen Faulkes (rules official), 11 June 2007
If I am playing against someone who just brought out a card that is unique that I know I have a copy of in my deck. Can I use Dark Harmony to remove Unique so that I can bring my copy of that Unique card out?
Works the same as Singular in that regard; see here. Yes.