I'm not sure there's anything " natural" about playing a musical instrument! And a so called " comfortable" way of holding an instrument - in the initial stages of learning - is not going to be the best in the long run. As a guitar teacher, I believe the " lefties" belief that holding the the guitar " the other way round" is best for them stems from the first contact they have with the instrument. I have observed that this "first contact" always involves the player wanting to run their " best hand" over the open strings. For a "lefty", this is of course their left hand. BUT I'd always advise lefties to play orthodox.