I'm all for not robbing, no taking something just because its owner wasn't careful to hide it enough or whatever. That's a no brainer.
However, a Kobo representative never comes to that thread telling us what codes are in use at a given time. Usually it's known through a website or a blogger, like it was for the bargainmoose code (multi-use). That's how they let users know about the discounts. And they expect the word will be spread.
Sometimes, they send an email. But in France, we never get those since French (e)books don't allow the use of coupons. However, many readers buy books in more languages than their native one (see a thread on that topic). So yes, we can use codes but on specific books only.
Without those forums, websites and blogs, I wouldn't even know what a Kobo coupon is and I would do most of my purchase at Amazon without a doubt.
edit to clarify things and correct spelling mistake
