I had a nonrefundable standard GLON points booking which couldnt be cancelled online (obviously, as it was nonref). I phoned Diamond Desk and they just reiterated the nonrefundability. I emailed the hotel asking to cancel and they did so; and points refunded instantly.

So firstly, as mentioned above, in theory points are only recredited where the booking T&Cs allow. Secondly i dont know why folks are saying hotels cant refund points.