I see what he said as borderline criticism. It is also important that he writes from private instead of a place where everyone is. Likewise, you too can give answers that will not exceed the limit to him.
Example : Just like him, from private message you can tell him "you looking so dumb". Or you can use block chat to block incoming messages from him. If we could send notifications to players' screens, I would warn him, but we don't have such a system. Sorry for this.