QUOTE: “For years, the user experience has been tarnished by irritating and intrusive ads. Thanks to extensive research by the Coalition for Better Ads, we now know which ad formats and experiences users find the most annoying. Working from this data, the Coalition has developed the Better Ads Standards, offering publishers and advertisers a road map for the formats and ad experiences to avoid.” Kelsey LeBeau, Google 2019
QUOTE: “If you have comments on your site, and you just let them run wild, you don’t moderate them, they’re filled with spammers or with people who are kind of just abusing each other for no good reason, then that’s something that might kind of pull down the overall quality of your website where users when they go to those pages might say, well, there’s some good content on top here, but this whole bottom part of the page, this is really trash. I don’t want to be involved with the website that actively encourages this kind of behavior or that actively promotes this kind of content. And that’s something where we might see that on a site level, as well.” John Mueller, Google 2016
If you have a commenting system (like Drupal, Joomla or WordPress) that allows for search engine friendly links (commonly called dofollow links) from your blog or site, you will probably, eventually be the target of lots of spam, be complicated in tiered link schemes and potentially fall foul of Google’s webmaster guidelines on using the attribute in certain situations.