I sense some bitterness in the comment. What makes or doesn't make the front page depends on a lot of things and it will not be the same every time. It will, for example, depend on other competing stories. There is a steady influx of new members. So stories that are old hat may not be so for a large section of HN visitors.

Yes, this was a Wikipedia link and Kalman filters has been discussed here many times, that said I found the discussion and commentary quite delightful.