I haven't noticed any flicker in my Aura, even with the setting pushed down to 1%. However, I have seen comments in the developer subforum that pushing the brightness of the Glo too low does result in flickering so maybe this sort of thing is more noticeable to some people than others. (Note: they were pushing the brightness lower than Kobo's software allows. That's why it was in the developer subforum!)

If the flickering is noticeable, I would definitely insist upon an exchange or refund.