Stablecoins like Tether (USDT), which is already a major participant in the $1.1 trillion commercial paper market, may bring new risks into short-term securities markets, according to Fitch Ratings, a worldwide ratings firm.  The rating agency had already issued a warning in July that stablecoins had the potential to destabilize credit markets in the short term. Tether has recently agreed to pay $41 million in a settlement with the US...