I noticed this with the Koi Nami skin. Not sure if it's the same with the default skin though.
If you notice; there's a line at the top of her that cuts off the outlines to her skin. Probably not noticeable to all but now that I do see it it really bugs me.
The New default Soraka does this also when she's in shrubs.
© 2014 Riot Games, Inc. All rights reserved. Riot Games, League of Legends and PvP.net are trademarks, services marks, or registered trademarks of Riot Games, Inc.