By default, you could make all new accounts unable to post comments on existing nodes until they've had a new node of their own approved. That would weed out all but the most dedicated spammers without forcing more work upon the admins. This isn't a fully automated solution, but it also wouldn't impact the legitimate users of this site in a negative way.
It would have affected me. When I first joined this site, I posted nearly 20 nodes in replies to other comments and questions on SoPW, before I posted my own question here.
My suggestion is that the first few posts by new Initiates should go through a manual approval until the user is promoted to Novice. The moderator should have three choices: Reject, accept or immediately promote to Novice. If the user gets three rejects then their posts are hidden and their account locked. If they post something good as their first post, then the promote button lets the moderator give them an immediate +20 XP bonus, so no more of their posts need moderating. While their post is awaiting moderation it is viable only to those eligible to moderate it. (Friars and above). This means that visitors to our site and the googlebot will not see any spam.
My other suggestion is that spam posts should be hidden more. The current This node was taken out by the NodeReaper... display takes up as much space as a normal node. I think it should shrink to a single line, or hidden entirely unless you select a "Show Spam Nodes" option in your preferences.
