I think he didn't make it clear enough. The system isn't broken, the original source just has a lower pagerank.I fail to see where the issue is. I've seen links rank lower than their relevant HN or Reddit posts on Google before.
Actually a sub domain is considered a different domain with it's own page rank, I believe this is do to many hosted blogs at wordpress, blogger etc...
The thing is, the pagerank should not matter. What you want when you search the internet is a relevant result, regardless of its pagerank.
If the system relies too much in the pagerank to determine whether a site is relevant to your search terms or not, well, yes, the system is broken.