My wife often asks me to edit her writings in linguistics. This is an interesting exercise, as my knowledge of linguistics is probably sufficient to get me a D+ on a Linguistics 1A final. And most of that limited knowledge is derived from the works I have helped to edit. This makes me very good at finding sentences that are not crystal clear, but very bad at knowing whether the lack of clarity arises from my lack of knowledge. The result is that Iris's writing ends up being much clearer to the non-linguist (or at least to me) than most technical writing is to non-experts.
Perhaps all academics should be encouraged to have their work edited by a practitioner of an unrelated field prior to publication.