Dominaria Spoiler Digest - Who's Who and What's What from the Release Notes
Choose a nonland card name. Target player reveals his or her hand. Thought Hemorrhage deals 3 damage to that player for each card with the chosen name revealed this way. Search that player's graveyard, hand, and library for all cards with that name and exile them. Then that player shuffles his or her library.
5/1/2009 The card is named as Thought Hemorrhage resolves. Spells and abilities can’t be cast or activated between the time a card is named and the time that Thought Hemorrhage has the rest of its effect.
5/1/2009 If the targeted player has multiple cards with the chosen name in his or her hand, the damage dealt by Thought Hemorrhage is all considered to be the same instance of damage. A single effect that prevents “the next time a source would deal damage,” for example, will prevent all of it.
5/1/2009 Thought Hemorrhage has no effect on cards on the battlefield that have the same name as the named card.
5/1/2009 The cards you’re searching for must be found if they’re in the graveyard, because that’s a zone everyone can see. Finding those cards in the hand and library is optional, though. This is true even though the targeted player has revealed his or her hand.
2/1/2014 If you target yourself with this spell, you must reveal your entire hand to the other players just as any other player would.