I have been thinking it would interesting to do the following experiment. Pick two random new posts and show them directly on the home page for a fixed amount of time. Feed the data from those posts (views, votes, content, comments) into some neural network which can magically learn what kind of posts generate most interest.
Showing random, new posts on the home page provides equal viewership to the experiment set while removing the age bias. Many candidate posts will likely be low quality, but we can expect people to filter them out and participate less in them. High quality posts will organically attract people's attention and the algorithm can over time learn factors that differ between lower quality and higher quality posts.
That definition of interest is basically what Reddit does, and in the end I believe the kind of manual curation the HN mods do ends up fostering a healthier and more interesting community. Neural networks fed by votes, views and comments tend to lean to promote outraging content.
Reddit and even HN currently I believe do not account for age bias. Upvotes have a cascading effect and posts which happened to get a few votes early tend to out compete all other posts. What I'm suggesting is to have a small quota on the front page purely for experimentation. These experimental posts do not need to compete with other posts for visibility and the outcome from them can be used to calculate interest. Since these experimental posts are only competing with posts within the experimental set, there is fairness with respect to age and viewership.
Showing random, new posts on the home page provides equal viewership to the experiment set while removing the age bias. Many candidate posts will likely be low quality, but we can expect people to filter them out and participate less in them. High quality posts will organically attract people's attention and the algorithm can over time learn factors that differ between lower quality and higher quality posts.