I do understand how difficult it is to deal with spam, and how important it is. I also see that the issue have arised from error/negligence and not from malice. But blocking the whole google account including the email, that can contain very important or urgent information, is completely unacceptable.

A small site like HN can block someone by mistake then apologize and say "Yeah, we definitely fucked up there", but google pushes gmail to make it essential for everything: login to phone, login to chrome, built in password manager in chrome, oauth login to third party sites. So it must handle things much more carefully.