Is there anything wrong with the CEO forwarding an email, adding just a question mark? It is shorthand for "Can you please tell me what is going on here and how it can be taken care of?". It isn't like if he typed out a whole sentence, it would cause the person who panics at a "?" to somehow not panic. They'll probably just read too much into the sentence and panic even more.
As someone who was on a team that got these "?" emails quite a bit, it isn't the email that was the problem. It was the culture that you will drop whatever you are doing to answer this one very specific question that was the problem.
Now my team had a very good manager who knew the system and pipeline. So if he was 95% sure he knew the answer, we never got the email. If he didn't, he would forward it onto the oncall. And the oncall might forward it onto someone else if they were busy with a Sev1/2 issue.
But it was expected that you would drop what you were doing and answer. I've seen devs get up during the middle of lunch and go back to the office to answer a Bezos question.
If you're asking someone to look into something, putting a "please" in there somewhere would probably be considered a bit more polite. Or are CEOs too busy to treat their employees like actual people as opposed to APIs for processing e-mails?