Here are 2 suggestions for the sift, not sure if they've been mentioned before:

1. Have a 'watch this post' option where you can watch any post, even if you haven't submitted it. You receive an email whenever it gets published, discarded, new comments...

2. Have a reward system for good / funny / intelligent comments. This would act as an incentive to make comments even more enjoyable. I don't think I'm alone in saying that I enjoy the comments almost as much as I enjoy the videos and its what distinguishes the sift community from youtube or metacafe. You could even have a 'best comment thread of the month' reward, with each commenter getting one free published video (like the *quality thing here on sift talk) for their contribution.