Answers so far (and what these services ought to deliver):
- Disqus Profile (full ownership on Disqus enabled sites, claiming authorship on others)
- Intense Debate] (for blog publishers: tightly integrated into the WordPress blogging platform)
- BackType Connect Plugin (for blog publishers: copies comments (that link to one of your posts) to your blog, no matter where they are on the web)
- Gravatar (self-promotion, better visibility)
- Google Sidewiki (adds another layer)
- become a blog publisher
In addition, here are some other services:
- co.mment (conversation tracker)
- coComment (conversation tracker - still alive and kicking?)
- Google Reader: "Like" item action (appreciation feedback)
Convenient solutions for ordinary netizens preferred.
For your reading pleasure:
Comment ownership is a complex problem. The commenter writes the comment, but the blog owner hosts it. So of course, the blog owner has the right to decide what he agrees to host or not. But the person who wrote the comment might also want to claim some right to his writing once it’s published.
("Who Owns Your Comments?" by Stephanie Booth)