Yes it is off topic unless you identify a specific source of concern.
I don't understand why you think the point of the original question is clear as I see only one point in your question.
It was posted in Lang-8, where native English speakers are supposed to
correct it if necessary. However, no one corrected it.
Does it mean that in Lang-8, all ungrammatical sentences are corrected and changed to perfectly grammatical sentences by native English speakers? How can you be so sure?
It sounds like since it was not corrected in Lang-8, the sentence must be fine. How do you know?
Our guideline clearly states "Proofreading questions ("Is this correct?", "Are there any mistakes?") or critique requests are off-topic unless a specific source of concern in the text is clearly identified."
You didn't specify any source of concern.
BTW, what on earth do you want to mean using the sentence? How come "more difficult" and "nobler" could be placed side-by-side? If the original sentence comes from an essay written in Japanese, don't you think it should be checked whether the translated sentence makes any sense at all?