Those kinds of tags are too broad. I was thinking of some javascript to let you highlight subparts of a comment then tag it with a more specific label, like "Straw Man Argument."
People would probably view the comment differently, but readers (and the author) could then see 60% of people thought part of his comment wasn't useful. Ad hominem and straw dog attacks, for example, might be unintentionally inserted in the heat of argument. Right now, comment rating is very blocky.
Make it so you can tag arbitrary pages from within your browser, and other people visiting the page can see the tags if they wish. Imagine the fun of doing this with the New York Times, Wall Street Journal, in addition to blogs and discussion forums, etc. etc.
People would probably view the comment differently, but readers (and the author) could then see 60% of people thought part of his comment wasn't useful. Ad hominem and straw dog attacks, for example, might be unintentionally inserted in the heat of argument. Right now, comment rating is very blocky.