I just wish they added (and enforced!) a distinction between transactional notifications and everything else.
Whenever I see a spam notification, I immediatelly go mute the channel and the problem never repeats itself.
If you want to know when your audiobook is downloaded or when you get a your next credit is available, you also have to put up with promotional "X book is 40% off" garbage spam.
There's nothing to force you to be honest. It only forces you to specify a channel when you post a notification. You can as well just create a single one for everything, which is exactly what some apps do.