Moderating comments can be a real pain in the proverbial, however, if you don’t, the pain could be greater. Blogs are fairly well covered with anti spam tools like Akismet but like everything in life, it is not perfect. If a comment happens to sneak past Akismet or any of the other anti-spam tools you use, you may not notice it, or its effect, for quite sometime.
SEOGadget reported a sudden and unexplained drop in search traffic which was only resolved once a couple of very spammy comments had been removed. What is interesting in this situation is that although the comments linked to some fairly doubtful sites (sex related), the links were nofollowed.
We know that Google does follow nofollow links, even if it doesn’t pass any rank or count them as actual links. In theory, the nofollow tells Google “I don’t trust this link” so the nofollowed link should not have been the problem (at least not if Google is telling the truth about not placing any authority on nofollow links). From this, it could be assumed that the text that was used in the comment had caused the problem.
The reason, while interesting, is not the issue here. The issue is that those comments got through the spam controls put in place. Comment moderation is one tactic that in 99% of cases, cannot be bypassed.
When moderating comments, there are two issues that need to be addressed. Are the comments themselves in anyway doubtful and do they link to spammy or doubtful sites. Answer yes to either of these then delete the comments completely.
Comment moderation is time consuming and can be a hassle. However, trying to find why a page has suddenly dropped from the top of the search results can be an even bigger hassle. Find the time and cut off the comments before they harm your site.
On a side note, if you read through the post on SEOGadget, one thing should strike you. The use of Google Analytics was a huge help in trying to find why they had lost so much traffic. For a web analytics tool that is free, it can certainly provide a lot of useful SEO information and save a lot of time when trying to track problems.