Isn't it quite ironic to see the article suggesting that HN top link might include Medium post. I've usually read not-so-positive feedback about Medium posts. Isn't it the case?
Since anyone can write for medium, and anyone with an HN account can post medium links here, there are huge amounts of medium content. So we see a lot of that 90%, as well as the 10% that's useful.
Articles on Medium range from quite insightful to clickbait junk, as is the way of most open-ish access platforms.
A publication's "editorial voice", ranging from grammar and typography, to selection and discussion philosophy, are significant. There's a reason we see things as "New York Times" or "Fox News" or "Mad Magazine" or "Cosmo" or "The Economist" or "Soldier of Fortune" in voice or tone.
This is harder to pin down with blogs and social media, though distinctions can emerge, whether through self-selection, path-dependency, gross scale, algorithms, or some combination of the set.
Prejudice can be misused, but its advantage (to the judger) is that it makes judgement cheaper by reducing the set of what needs to be considered, at least for an initial judgement.
That's characteristic of any domain in which there's an information overload, or in which distinctions are subtle and difficult to identify initially. And argument, by the way, for dealing with copious information less by enhanced processing and more by expedited (and cheap!) discarding heuristics.