The problem with the ignore list is that you still see the responses from others. A scoring system like that in slashcode allows the community to filter, so the trolls don't get seen. They don't actually go away, but he quality of the user experience for everyone else goes up dramatically anyway.
Anyone interested can read about such approaches here:
http://en.wikipedia.org/wiki/Slashdot#Slash_and_peer_moderation
It's proven. It works. It would be a huge PITA for the POA admins to switch software in order to gain such benefits. Such is life.
I'd say the jury is still out or even that slash and stuff like reddit and dig are actually failures, unless you're looking to end up with a fairly homogenous group at the end. Various sites like slash, digg, and reddit have specific community leanings that are unnaturally sustained through their moderation systems.
And example is the iconic "TL;DR" on reddit. You're on a website that espouses to be full of hard core READERS, and yet, the TL
R crowd became the social norm there? Funny stuff if you think about it.
I'd say that any forum I've ever been in that automated ratings, ended up subtly changing toward a particular majority crowd's particular groupthink style.
Free for all type places rapidly degenerate into "let me delete 80% of this stuff and then I'll start reading".
Only moderator driven forums have ever seemed to stand the tests of time for general civility and the occasional mistake in judgement. It's really the most similar model to real life... the most diverse without harm to many individuals over long periods of time.
A few moderated sites do turn into personal bashing by moderators, playing by their own rules, but those usually die a fairly quick death, because they're so obviously toxic to real discussions.
The concept of an SZ here is brilliant. Allows those who want to participate in off-topic debate, to do so, while allowing the general participant to not see much of it. I wish we'd thought of something similar on some of the electronics forums I used to spend s lot of time on. Would have helped with moderator burnout and sanity on a couple of those forums, too.