In the end, I have a small question about this part: We generally do not moderate posts this old for on-topicness -- shouldn't it be off-topicness instead of "on-topicness"?
I think the sentence reads fine as is. It's the "issue" that's being referred to (in the sense of "a matter of discussion"), instead of the "problem", I think (i.e. if you replace
on-topicness with
off-topicness, then you'd also have to replace substantiveness with
non-substantiveness).