Oh man, I really feel for you. I ordered an Aura HD direct from their site and it arrived a few weeks back. As soon as I turned on the backlight, I noticed a brilliant white spot in the middle of the screen that was incredibly distracting. After searching online, I found this forum as well as many other pages mentioning this defect.
That's not a big problem, I thought. I'll just return it for a working one. Wow, that's a mistake. After three weeks, I'm still nowhere. First, I had to go through the "send us a photo of the defect" rubbish. After that, a few more round trips of frustrating support (like them asking me for a whole load of information about the device and myself that they already had because, as I mentioned to them initially, it was purchased through their site). Eventually, I said they could just send me any color as a replacement (mine was Ivory), just as long as I get something.
They gave me a Fedex waybill, asked me to return mine and said they would ship a replacement "in a few business days". And, because I'm a complete sucker, and believed that they would send a replacement, I actually sent them the defective unit back.
That was two weeks ago. They've got my defective Aura, and I have nothing.
Since then, it's radio silence from them. I replied to the ticket twice and they just ignore it. I speak to the online chat team and they said someone would contact me within 48 business hours. Nothing. At this point, I'm sending them back the cover that I purchased from them at the same time as the Aura and getting the credit card company to reverse the charge.
So, I'm afraid that I can't offer you any advice. Hopefully your experience will be better than mine. For anyone who hasn't yet purchased a Kobo device, please think about it long and hard beforehand. Their support isn't just bad. It's unbelievable. I've been ordering online since since the early days of the Internet, and this will be the first time in all those years that I will have to reverse a credit card charge. That's quite something.
One other bit of advice I can offer to anyone with this defect who might be thinking about returning it - Maybe just learn to live with the flaw and next time buy another device. I don't think it's worth engaging Kobo support about it. Better to have a defective device, rather than nothing.