Believing that comment spam affected the entire blogging community, in early 2005 Google's Matt Cutts and Blogger's Jason Shellen proposed the value to address the problem.
Prior to this, webmasters would place nofollow tags on some of their links in order to maximize the PageRank of the other pages.
[7] However, as of March 1 2020, Google is treating the nofollow link attribute as a hint, rather than a directive, for crawling and indexing purposes.
More sophisticated server software could suppress the nofollow for links submitted by trusted users like those registered for a long time, on a whitelist, or with an acceptable karma level.
Google employee Matt Cutts has provided indirect responses on the subject, but has never publicly endorsed this point of view.
[20] The practice is controversial and has been challenged by some SEO professionals, including Shari Thurow[21] and Adam Audette.
Several Google employees (including Matt Cutts) have urged Webmasters not to focus on manipulating internal PageRank.
Google employee Adam Lasnik[25] has advised webmasters that there are better ways (e.g. click hierarchy) than nofollow to "sculpt a bit of PageRank", but that it is available and "we're not going to frown upon it".