I came across a trick that’s been used by blog comment spammers in the hopes that they receive a back link on popular blogs that receive traffic. This trick is used on blogs that allow previous commenters to post comments without being moderated, something many bloggers prefer rather than having to moderate all comments.
Spammers will post a comment that is related to the topic in discussion. While the comment may or not be entirely on target, the post is generally on-topic enough that it doesn’t raise any red flags to the blog owner. The blog owner will approve the comment, and with that approval, the spammer will have gained access to post unmoderated comments carte blanche using the email address with which he signed up.
Although many blog administrators will see subsequent comments, including the URL, they can be easily missed, especially when a blog receives many comments. It’s amusing to see spammers try this method, especially because their keyword names are usually dead give aways, and most blogs use “no follow,” preventing them from receiving any search engine benefit.