In my WordPress Wishes post, I mentioned something I thought would be cool: the ability to "feature" or "bury" comments. This would be very simple, just a few extra links when viewing the comment moderation list in the Admin area.
The result would just be extra CSS class names applied when the comments list is output. Utkarsh Kukreti came to the rescue! Here is his announcement post and the plugin in the repository.
I explained my thinking on all of this in a post on CSS-Tricks: Curating Comment Threads. There you'll find screenshots of how the plugin works, and my first exploration into using it.