On the subject of authenticated commenting, the Invisiblog anonymous weblog publishing host uses signed entries to make sure you're you, in spite of all entries being sent through Mixmaster anonymous mail network. Sounds like a plan to me--though that raises the bar for use, since you need PGP or GPG to sign your post. Other than that it's pretty similar, really, except it's for weblog entries instead of comments. (Link by way of Christian Crumlish, I think.)
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It’s just like FreeNet. Only with a readership at the expense of a few points of vulnerability.