Random ideas braindump

A first thing could be to add a "report spam" button on recent comments (for instance, written on the last few hours) to subscribers. This could put the comment on a "to review" queue, which the moderators could then look at. Most of the content of this queue would be spam (and for people who persistently report non-spam as spam, you could disable this feature for them, to reduce the noise in that queue).

Another option would be to allow subscribers with old enough accounts (something like members of the site for X years who posted at least Y comments) to directly hide spam comments (again they would go in a queue for a moderator to review). A related option would be to allow for these subscribers to vote for hiding the comment; after a number of votes it is hidden (the number of votes would have to be hidden for non-moderators to prevent abuse).

You could go even crazier and do a bit of "meta-moderation" (a bit like on slashdot): allow people to see the queue of comments flagged as spam, and allow people to mark whether the flagging was correct or not. You could also allow people to mark comments as not spam (but this could be abused by the spammers themselves).

And you could even go the full crazy, and start computing trust metrics on each poster, IP address, and network, based on past history (even things like "user X has been often flagged as non-spam by user Y, which has a high trust metric, so we also increase the trust metric for user X"). You could adapt naive Bayesian filters from email anti-spam solutions (not to block comments, but just to flag them for moderation). You could combine both and use trust metrics as a feedback to the Bayesian filter. You could show the "score" from the filter as a border color for the comments, updating them based on subscriber feedback. And so on and on.

The common thread of all these ideas is to use the community itself to help with the filtering, and do so in an unobtrusive way (if I am reading a thread and see a spam comment, it is natural to reach for the "kill it with fire" button, especially if there is one nearby). It might use only a few seconds for each subscriber, and in a natural way since we are already reading the comment thread (and not having to go out of our way to use a separate system only to fight spam). A "recent comments" feature (if there isn't one already) can help even more (and be a useful feature on its own).