How many times has WhatsApp been blocked in Brazil? What's your advice for those 100 million users when it stops working? Switch to another centralized messenger, and convince their friends and family members around the world to do the same so they can continue communicating?
What would happen if e-mail didn't exist, and a site like HN listed their WhatsApp contact information instead of an e-mail address? Suddenly, the Brazilian user base here would be unable to contact HN. They might be completely out of luck, or if the user base was large enough, HN could add an alternative contact method for users in restricted regions. "Contact us on WhatsApp. If you're in Brazil, you'll need to contact us on ABC messenger instead. If you're in China, and unable to access both, you'll need to send us a message on XYZ messenger."
What would happen if e-mail didn't exist, and a site like HN listed their WhatsApp contact information instead of an e-mail address? Suddenly, the Brazilian user base here would be unable to contact HN. They might be completely out of luck, or if the user base was large enough, HN could add an alternative contact method for users in restricted regions. "Contact us on WhatsApp. If you're in Brazil, you'll need to contact us on ABC messenger instead. If you're in China, and unable to access both, you'll need to send us a message on XYZ messenger."