I'd like someone to look at all the different commenting systems out there, and work out why some of them have a decent proportion of interesting discussion, while some of them are full of pond scum.
And then write up the findings, along with a nice simple checklist for "How to manage the comments on your site if you want good discussion".
Because, frankly, on 95% of the sites out there I avoid reading the comments, because I know it's just not good for my blood pressure.