Sites like HN and Reddit are aggregators in the literal sense. They take a large volume of data points and reduce it to a select few that get shown to most users. that aggregation function is "most interesting", not "most representative". Those are direct opposites of each other: interesting is almost by definition unusual.
I always find the subreddits that try to explicitly not target polar extremes the most fascinating from a sociology perspective. For example, this photo of a sink faucet is the most mildly interesting submission of the past year:
Does that mean all other submissions were less interesting, or less mild?