Well I dont really know for sure if Gaara tattoo'ed the kanji on his skin. I just think when he got all emotional there he got for the first time a pretty decent control over the sand hence why it might have been his skin and his blood. When Gaara gets hateful/murderous/angry/sad/excited he might have it easier to control the sand and the spirit, and still has him beeing pretty sealed in with him self. It doesnt matter that much it was a really cool paralell to his past that he tattoo'ed the mark of Love on his forhead.

Now after the story buildup I so want to see them clash. And also some progress on the Orochimaru vs Hokage fight.