At least it’s better to downright remove this API than do what happened to whispers and add spam filters which block everyone but some users who can actually send whispers without getting cryptic errors or the interface just not working. 
Whispers broke and you can’t receive PMs from what Twitch considers strangers, only way to fix it is to either give them mod powers in your chat or follow them. Great that the create/delete API for follows doesn’t fucking exist anymore.