Just so we’re all clear about this, the convenience of the CommentAPI, that nifty little service that allows users to make comments to your blog from the comfort of their favorite RSS aggregator, comes at a cost. Enabling the CommentAPI supplies a back door for comment spammers who want to bypass the CAPTCHA guard posted at the front door.
I was just chatting with Andrew about this and we realized it would be quite easy to add CAPTCHA support to the CommentAPI if we could get both RSS Aggregator developers and blog engine developers to agree on how to update to the CommentAPI to support a CAPTCHA image url or a CAPTCHA text question. The RSS Aggregator would then display this image or text, and provide the user a field in the comment dialog to supply the answer to the CAPTCHA challenge, which the CommentAPI would validate with the CAPTCHA control. Of course this wouldn’t close the CAPTCHA backdoor for Trackbacks and Pingbacks.
In the meantime, I tend to favor non-CAPTCHA approaches to comment spam filtering for this very reason. I want to fight comment spam tooth and nail with every resource I have before I turn off the CommentAPI on my blog. Likewise, I still support Trackbacks because I personally have found them more beneficial than detrimental so far.
In any case, Subtext will provide configuration options to turn each of these services on or off individually so that users have full control of comment entry points.