Wow... I was absolutely sure that this backfire story WAS the April Fools' joke. It just seemed so farfetched. The animated gif I could understand, but actually blocking all future replies? That's where I figured that nobody would ever actually implement something so stupid and dangerous.
Yes, it's the side effects and real world changes to outgoing mails that is just beyond stupid and uncharacteristically bad even for Google April Fool's jokes. I don't even understand how the mere idea could be approved. It's like if they got an intern to "come up with something fun".