I kept it simple: Reverse order = Number of points
i.e. #3 on front page = 28 pts etc.
Points are accrued every time a snapshot of the front page is taken.
There is a flaw with this system in that outside of peak hours, some less important item might hang around the front page a little longer and earn a too many points but I feel that it still works well enough to catch up with HN Content.
Respectfully, I disagree. The points are clearly correlated with how high the item gets, and how long it stays on the front page. As such, I think the ranking is of value. It also has the merit of being simple to compute, and easy to explain.