s'io credesse che mia risposta fosse A persona che mai tornasse al mondo, questa fiamma staria senza piu scosse. Ma perciocche giammai di questo fondo Non torno vivo alcun, s'i'odo il vero, Senza tema d'infamia ti rispondo.
If I believed my answer was to a person who'd ever get back to the world, this flame would keep still without moving any further. But since from those undergrounds no one has ever come back alive, if I hear what's true, I answer you without fear of infamy.
I don't think I agree - the meaning doesn't change with the change suggested by Guilon and although his suggestion is more common in English I think Goncin's stays closer to the original. I must admit I have no idea about how commonly used the original is in Italian.