I was thinking of using WordPress for a project and was suprised at the omission of these following two features.
Firstly, that commenters can't have a comments tag cloud. Once this feature is in place it could be used with the second feature that I have noted as missing, for custom comments queries.
Secondly, that comment's can't be seperated out from the blog post into their own page. There are a number of reasons one might like to do this, such as querying the comments if you happen to be looking for a particular commment/commenter, or in conjunction with a tag cloud you could find comments with particular tags.
From what I have read, this isn't currently feasible via the plugin route due to the nature of the current blog construction.