Apart from stereo width, why do people hard pan Left and Right when doing double tracking? Why not 50L & 50R or somewhere between? Is it because of phase cancellation?
I think hard panning as opposed to 50%L/R is just personal preference - nothing to do with phase cancellation.
Obviously with hard L/R you will get a wider stereo sound-stage - I think it just depends on what you want in the mix. You can also try and introduce some chorus and delay to give you even more depth to the sound.