These days Japanese exchanges have stricter order validation, e.g. orders with price outside a certain range are rejected outright, and if actual trading takes

These days Japanese exchanges have stricter order validation, e.g. orders with price outside a certain range are rejected outright, and if actual trading takes the stock price to (say) 75% of its opening price, the trading for that symbol is halted for the day. So the Mizuho blunder couldn't happen again today.