Comment spam is the bane of one's life on the internet; there's probably some underneath this very post (if there isn't, there will be). Spammers post little messages with little relation to the content above, and link to their, generally scammy, site.
The intention isn't really to trick individuals to click on the post, because even spammers know that people don't tend to be that intrigued. Instead, it's to game Google Search rankings, which are determined by the number of sites which link back to yours.
For quite some time now, Google has deliberately ignored links in comments, knowing that they have nothing to do with the owner of the site. That hasn't stopped the spammers, of course, who aren't known for making sense, but it has at least dampened their effects. But recently, it went one step further, and started actively penalising sites which engage in spam.
All of which led to the American politics site, TPM, receiving a cease-and-desist letter from a spammer, asking them to delete previous spam from their site. Josh Marshall, the editor, writes:
In other words, the estimable businessmen and women at realinsurance.com.au have been paying SEO companies to spam the comment sections of sites around the globe. But now Google’s new search algorithms are making that legacy spam really damaging. So now they’re sending out cease and desist notices to the victims of their earlier spamming demanding that they search their archives and remove their spam.