> For example, the biggest country-wide payback program is payback.de, and their most of their coupon multiplier links here – https://www.payback.de/coupons/info – will be clickable, but silently not work after you purchase.

I don't understand this claim. Payback coupons have to be activated before purchase, so even if somehow that link wouldn't work anymore after a purchase it'd be too late anyway to have the coupon applied.

Can you elaborate or provide links for more information?