Next to each comment author's name are two links: Ignore Author, and Read More.

Ignore Author helps you ignore the posts from an author. Click on that link, and from that point on, you won't see that author's posts. (You need to refresh the page for it to take effect.) It functions at the individual level. Try it, and it should make sense.

The Ignore Author feature isn't censorship. By ignoring an author, you're the only person not seeing his/her posts. Other users will still see the post.

Read More helps you search for posts from the author. This is useful if you like a writer, and want to read more from the writer.

The goal of these two features is to discourage flamewars, and encourage better posts and more consistent identities.