Six Apart communicates about Comment Spam, at last! They are still working to find a solution, they dismiss registration (upcoming feature but different usage), as well as comment moderation and image comprehension technology, and point to MT-Blacklist as a solution.
I'd like to suggest an additional option: simple comment authentication. It works like this:
- a visitor to your weblog leaves a comment along with an email address (mandatory) and an optional URL
- the comment is displayed immediately but any URL it contains is either turned into non-clickable text or replaced by a placeholder (like [*]), rendering spam for GoogleRank ineffective
- an email is sent to the email address provided, asking the visitor to click on a confirmation link to authenticate the comment and activate URLs (if any)
- once the weblog receives the confirmation, it activates any URL present in the comment. The confirmation page may offer to the visitor the option to save a cookie to allow for "One-Click Comment™" ;-)
This system has the following advantages:
- it provides a comment authentication feature that does not require a complex system nor anything beyond your weblog system
- it effectively ensures that visitors leave a real email address. One issue though: email@example.com may require a blacklist of names that cannot serve as valid email domains
- compared to a registration system, it is significantly easier (requires only one click, no name, no password) and less "in your way" (the comment is immediately displayed for the sake of synchronous conversation, just without clickable links)
- it scales, the (small) burden is entirely left on each visitor commenting
- it can add bonuses, such as offering the visitor to subscribe to a notification email and receive all other following comments by email (great for keeping trace of comments left on others' weblogs)
- it can work along with other anti-spam features (such as IP banning, URL blacklists, etc.)
The reasoning beyond this system comes from my quest for simple comments authentication and precisely the fact that, considering that my weblog is not a public space but a personal space that I open to others, and that I do not publish anonymously, I have little or no interest in receiving anonymous comments.