NEW YORK (Reuters) - The rules of Treasury auctions may not sound like the stuff of high-stakes diplomacy. But a little-noticed 2009 change in how Washington sells its debt sheds new light on America's delicate balancing act with its biggest creditor, China. (http://feeds.feedburner.com/~ff/reuters/topNews?d=yIl2AUoC8zA) (http://feeds.feedburner.com/~ff/reuters/topNews?i=TFhU1Exn_AA:9Gt4mHTIuac:V_sGLiPBpWU) (http://feeds.feedburner.com/~ff/reuters/topNews?i=TFhU1Exn_AA:9Gt4mHTIuac:-BTjWOF_DHI) (http://feeds.feedburner.com/~r/reuters/topNews/~4/TFhU1Exn_AA)