John Carney: CNBC
"There would really not be any additional inflationary pressures caused by a trillion coin" (original).
The key point here is that the government would not be throwing an extra trillion dollars into the economy. It would, rather, be spending exactly how much it planned to spend anyway. It would not be issuing bonds to cover some of that spending but bond issuance by the Treasury does not do very much (probably nothing at all) to combat inflation anyway. The amount of government issued financial assets remains the same, even though the composition of dollars and Treasury bonds changes.