Quoting Dries Buytaert <dries.buytaert@gmail.com>:
Five core modules directly query the node_comment_statistics table. In my view of the world, comments are first class citizens in Drupal. We should optimize how they interact with nodes. In other words, I agree that it makes sense to merge the node_comment_statistics table into the node table (assuming it does improve performance). It would also help eliminate bugs.
I have been reading the posts and wondering what is so different about a comment. A comment is nothing more than content very much similar to a node. As content it has a specialized content type which at the moment isn't visible to the administrator. So, I think to myself that perhaps a comment should be treated as a node and the comment table is nothing more than a one to many relationship mapper. I'll give this some more thought toward D-7 I can see this idea as enhancing many modules. Earnie