Translation:No one at the school had written about this.
If the hover gives sobre as on, why is written on this wrong? It's stilted English, but incorrect.
It's not even stilted - it is correct English.
Furthermore, unless I'm misunderstanding how to say it in Spanish, your trasnslation also accommodates a more literal interpretation of the Spanish sentence where "this" is a desk that someone wrote "on" (and neither "about" nor "of" work).
Thus, I think yours is a better translation than is either of Duolingo's.
Because the answer has to be correct in English too. Sobre is about in this case. Of course, you could say "on this topic," so I wonder why you wouldn't say "written on this."
You can say "I had never written on this" in English. He wrote on this theme in his seminal novel. on and about are fairly interchangeable in this context. So I think it should be right.
"No one at the school had ever written about this" seems like a very natural way to phrase it in English, I realize that the "ever" is not included here though and it might just be a grammatical error on my part.
Why is it 'escrito,' as, when translated to English escrito means 'I wrote' or 'they written' both which do not work for the sentence
"Nadie en la escuela" could be "Nobody in school", dropping 'the'? Wouldn't you need 'la' in either case?
"He had already suffered enough. I had never suffered so much No one at the school had written about this."
Yeesh, these sentences! O_o