Comment spamming hurt both sites ranking, says Google

Google Webmaster explain ‘how abusing comment fields of sites by putting up comment containing links is a bad and non-legit way of getting links to your site. “a link spammer might spend hours doing spammy link drops which would count for little or nothing because Google is pretty good at devaluing these types of links.” […]

Google Webmaster explain ‘how abusing comment fields of sites by putting up comment containing links is a bad and non-legit way of getting links to your site. “a link spammer might spend hours doing spammy link drops which would count for little or nothing because Google is pretty good at devaluing these types of links.” Those who’ve been penalized by Google for comment spamming are adviced: “go to your site in webmaster tools, click Links to your site in web section, and check for all suspicious incoming links. If you see a spammy link you created, try to delete it, else contact webmaster to remove link. Once you've cleared spammy inbound links you made, you can file a reconsideration request.” And to avoid comment spam hitting your sites: • Disallow anonymous posting • Use CAPTCHAs and other methods to prevent automated comment spamming • Turn on comment moderation • Use the "nofollow" attribute for links in the comment field • Disallow hyperlinks in comments • Block comment pages using robots.txt or meta tags.