I think you've got the wrong end of the discussion, there.
If you can't or don't want to turn you CRT off... then what's the next best thing for avoiding burn-in?
Send it a black signal, or send it a bright signal?
It's the black signal, because it charges the screen less. Charging the screen is what causes burn in. If you charge it less you get less burn in.
> Arguing that CRTs could display true black
Nobody argued this. Where did you think you read this? I said 'show a black image'. Send it a black signal. It's the minimum signal you can send it without turning it off.
Or just send it a random signal, such as static or even better, an aesthetic screensaver. Showing black on a CRT didn't save any power, and the computer stayed on anyways (since it often took 3-5 minutes to boot up in those days). Black could mean something is wrong or signal is disconnected.
If you can't or don't want to turn you CRT off... then what's the next best thing for avoiding burn-in?
Send it a black signal, or send it a bright signal?
It's the black signal, because it charges the screen less. Charging the screen is what causes burn in. If you charge it less you get less burn in.
> Arguing that CRTs could display true black
Nobody argued this. Where did you think you read this? I said 'show a black image'. Send it a black signal. It's the minimum signal you can send it without turning it off.