I think people are reading too deep into if throwing out objects in the light world is hypothetically killing/torturing the darkners.
It's not meant to be that literal. Darkners just want to fulfill their purpose, when they get old, worn out and thrown away it means they've done their job and are probably happy about it. Think of it like Buddhism.
There are exceptions-like books- that are worth preserving throughout multiple generations so discarding them would be bad. I don't think throwing out a busted radio would upset the radio-darkner, like it would be way more upsetting to it if you kept it on life-support forever instead of letting it live out its natural lifespan and end.
You also have to remember that the TV World fountain was created by Kris so the environment and even Tenna reflects their memories and feelings. Darkners personalities are malleable depending on who created their fountain.
In other words you're not meant to read too deep into it, I think Toby might explain this in the next newsletter so the autistic kids don't feel bad about throwing away their old toys or something.