There are only two times a runner can get hit by a fair batted ball and not be out. If the ball is deflected by a fielder, including the pitcher, before hitting the runner. On the URC thread you cited, I posted an extreme situation to drive home the point. I'll include it here. Ted Williams at bat, Bobby Doerr is at second.
Defense puts on the shift.
They take all fielders, with the exception of the left fielder, from the left side of the field and put them on the right side. Williams inside outs the pitch to the left side, it hits Doerr. Doerr is dead out as he limps off the field. So the Mgr comes out and says, Hey blue, There was no fielder there, how could he interfer. Answer, Doerr interfered with the normal course of play and didn't give the defense a reasonable chance to make a play on it before it hit him, that's interference.