On top of original demand, I would add the ability to move comments (and childs) inside a page from a thread to another.
I have users that often reply to the page instead of reply to comment and that gets messy.
I also support original demand as cleaning is necessary.

We would find it quite useful to be able to have more flexibility with comments. Currently, once a comment is added to a page, it is either stuck there or can be deleted.

What we are finding is:
1) some pages become popular and attract long threads of comments- often diverging in to multiple topics
2) some users just don't "get" Confluence, and so when they're trying to add some information, they whack it in a comment on the closest available page (even though it might have nothing to do with what they are commenting about)
3) Project managers need to troll pages to make sure that this isn't getting out of hand, and create new applicable pages, and then cutting and pasting comments in to appropriate pages

To solve this, it would be really nice (in order of usefulness)
a) move comments from one page to another
b) be able to move threads of comments to another page
c) have more flexibility with entry types, so a comment can be transformed to a page or news posting