Whether comment support is essential for blogs or not, I think blog comments can be improved on. Simple list of comments is just too flat and boring. And best comments tend to be buried in a pile of me toos, silly jokes, and troll craps.
I think post writer should be able to highlight comments they like so they stand out. Post writer should also be able to exile comments they don't like to a secondary unindexed comment page where comments from unverified commenters can go as well.
I also think post readers should also be able to 'favorite' comments, digg-in-a-bucket like.
Just dumping ideas to reduce brain fart before starting work. ;-p