From the post:
Apart from the content there are various features from metadata (like IP etc) which can help tell a spammer and regular user apart. Following are results of some data analysis (done on roughly 8000+ comments) which speak of another feature which proves to be a good discriminator. Hopefully this will aid others fighting spam/abuse (if not already using a similar feature).
(graph omitted)
The discriminator referred above is typing speed. The graph above plots the content length of a comment posted by a user against the (approximate) time he took to write it. If a user posts more than one comment in window of 5-10 minutes, we can consider those comments as consecutive posts. …
An illustration that subject identity tests are limited only by your imagination. From what I understand, very few spammers self-identify themselves using OWL and URLs. So as in this case, you need other tests to separate them.
A follow-up on this would be to see if particular spammers have speed patterns in their posts or searching more broadly, say across a set of blogs, a particular pattern. That is they start with blog X and then move down the line. Could be useful for dynamically configuring firewalls to block further content after they hit the first blog.
You have heard that passwords + keying patterns are used for personal identity?