PG&E, two consumer groups, and the city of San Bruno on Thursday all appealed a proposed $1.4 billion penalty against the utility for its role in a fatal 2010 natural gas explosion, and a state public utilities commission member also raised questions about the suggested penalty. The multiple appeals suggest a particularly combative process leading to a final decision by the state Public Utilities Commission about how much of a penalty and fine PG&E should pay in the wake of the explosion, which killed eight and wrecked a quiet San Bruno neighborhood.