Why not add a user setting - like Google does for censored results? You'd tick a box "Show less relevant / unmoderated comments" - provided directly on the discussion pages. You would tick that box at your own risk, knowing you may find offending comments. And if you find too much spam, and can't seem to enjoy moderated comments enough, just untick it and the spam goes away. This way you ensure moderation can't be abused for censorship purposes.