Lingering worries over America's soaring debt kept the Dow and S&P flat on Thursday as the Nasdaq inched up 0.28%. The U.S. 10-year yield hovered around 4.539%. Key stock names were Seagate, popping 4.24%, Tesla 1.92%, Enphase Energy -19.63% and Humana -7.58%. Coinbase jumped 5% as Bitcoin rallied another 2.6%