Yes, there's a grey area - I work in editorial and first came across the distinction years ago. I found it confusing because all my clients are making money from their publications (they're commercial). I think where a editorial use is distinguished in the terms from commercial use, it may be acceptable, but it depends on the terms, whether there's a distinction between the two. And also, whether the licencees consider Medium to be editorial... because they might want images to appear in the Daily Telegraph, but not necessarily on our blogs. Very grey area!