(I'm not sure there's any way to find the HTTP status code in a modern Firefox environment short of using web developer tools. It's not in places like 'Page Info' as far as I can see.)
I'm old enough to remember times before browsers showed 'friendly' error messages, and a 500 response from a server would display a '500 Server Error' message to the user. Users hated it. They'd panic and think they'd broken the website somehow. It was horrible from a support perspective, and if the user was new to the web it sometimes made them very anxious about using the web in the future.
Users have no business seeing error codes. Those are for devs. Hiding them away in devtools is a very good thing.
I'm old enough to remember times before browsers showed 'friendly' error messages, and a 500 response from a server would display a '500 Server Error' message to the user. Users hated it. They'd panic and think they'd broken the website somehow. It was horrible from a support perspective, and if the user was new to the web it sometimes made them very anxious about using the web in the future.
Users have no business seeing error codes. Those are for devs. Hiding them away in devtools is a very good thing.