(This February 14 story corrects typographical error in the seventh graph and removes the reference to the precise location of the apparent suicide) By Sarah N. Lynch WASHINGTON (Reuters) – U.S. federal judges were the target of more than 4,500 threats and other inappropriate communications last year, the head of the U.S. Marshals Service said on Monday, adding that his office is concerned about the rise of domestic extremism in America. “The increase in our judicial … threat investigations and inappropriate comments have been going up quite frankly for a couple of years,” Ronald Davis, dire…