What causes Feathering in motorcycle tires?

I have a Honda PCX 125 that the rear tire I have noticed has been starting to feather. I checked my tire pressure, it's at 40 PSI, which is where it's supposed to be. I don't feel any shimmies or hear anything out of the ordinary. I did take my bike to the dealer where I got it from and they said it could be my rear suspension. Could this be a factor in my tire wearing bad?

40psi seems high, are you sure that is what the manual says?

The first place I would look is at the wheel alignment but being a scooter that is non-adjustable, are you certain the frame is straight. When the tyre(s) were fitted was the wheel balanced, is there uneven wear around the tyre?

40psi is incorrect (extremely over inflated).
40psi is the maximum pressure allowed before damage to the wheel & tire were to occur.
Your owners manual, or the VIN plate on your scoot will show the correct psi.

It is normal wear pattern particularly on the shoulders