From now on, the site will be using CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) to filter out the undesired comment spam. The freely available reCAPTCHA service is being used for this purpose.
For the last couple of months the site has been receiving a lot of spam comments created by bots. The first solution was to enable comment approval. That however had some drawbacks: there was a delay between comment creation and publishing and the author received a lot of unnecessary notifications about spam comments.
The solution was obvious: using some sort of CAPTCHA.