A design rule for the display of any appliance with a clock: It must be possible to remove or hide the clock. I don’t need 10 devices to keep track of time for me.

Yes, please. I don't want a clock on my microwave, or my oven. If I'm not interacting with it, it should produce zero light.

(Some people use oven features that involve knowing an absolute time, such as "turn on at this time". That seems to be the uncommon case, and meanwhile everyone has to deal with a clock that's rarely right.)

Best they can do is blinking "12:00". Actually I encountered a kitchen appliance doing almost the opposite, after power off/on it didn't function before confirming any time.

Amen to that, I have a pair of built-in IKEAs, a microwave and convection oven, both with clocks when they're idle. But of course they're separate devices so they drift separately, which is obnoxious-looking. Happily the microwave did have a hidden setting to just display - - - - instead of the clock (though for no apparent reason the convection oven does not have that option, sigh).