But then people may have not like having their up-votes be so transparent..
It would help take care of the effect where older uses leave due to changing interests etc.
Note: I don't actually think it's a good idea. I think just figuring out _what_ you want exactly, in vaguely quantifiable role, is sort of a hard problem. I suspect a lot of people have different 'golden ages' in mind when they think of HN.
When I came here originally it was pretty startup heavy, which was sort of remote from what I was up to at the time. I liked it when it got a little away from startup business related stuff (my perception) and toward more generic technical issues. My point is even if everyone agreed that ait has gone done hill (an open question), not everyone might agree on what it should be like. It's not a democracy of course, but even as an individual for my own preferences that seems as hard as the technology issues.
I am not so optimistic about submissions because the data we currently have is tainted by submissions we don't want. However by using the technique you have described, we could probably achieve better results.
I think something like PageRank can really help. The same need is to rank things based on a directed acyclic graph. The only difference is we have multiple kinds of vertexes: users, submissions, comments.
Stackoverflow operates under this principle, more or less, but it doesn't seem to entirely stop the slow decline.
Call it undemocratic, but insight and perspicacity is not uniformly distributed so it's absurd that pg/$whoever_you_respect's upvote on an article counts as much as anyone else.
As a simple experiment, it would be interesting to see a view of the frontpage based only on the upvotes of people who are above a certain avg-comment karma threshold (since the site is predicated on karma as a quality indicator) and the idea that people who write insightful comments won't upvote crap stories.