Also the poster is essentially a kid. I would hold my judgement before flaming him fwiw.
Not to mention it's just a notification, who really cares unless it happens all the time which is just more of an argument to fix the platform behaviour. Some people are so high and mighty.
Don't blame the individual for an innocent mistake (we don't know if he knew that it would trigger 400k notifications). He is young and might be inexperienced, so we should be forgiving.
Think about why the system is set up in a way that an untrusted contributor can trigger so many notifications with a PR that is of little value.
That is a much harder problem to solve, so that is why some people go to the easy solution ("ban him, he is an evil bad person, gross social misconduct").