[Edit: Issues, Bugs, and Requested Features should be tracked at Google Code, not here -- matt, 2010-04-23]
Less Wrong is still under construction. Please post any bugs or issues with Less Wrong to this thread. Try to keep each comment thread a clean discussion of each bug or issue.
Requested features... sure, go ahead, but bear in mind we may not be able to implement for a while.
I'd've thought so too a priori, but Hacker News tried something like this, and people started worrying that e.g. commenting on old posts would drag their average down.
I guess a really good karma system would need a better theoretical foundation, and tweaking outside of that is a very inefficient activity. Possibly one of these is already described in the academic literature. Maybe one of the qualified members of our community could contribute the effort towards finding one or research it from the start.