Comment spam is unwanted posts under articles or in forums, usually generated automatically and carrying links to other sites. Google counts it as user-generated spam, meaning spam that users leave on a site through a channel the site provides.
Why does it matter for SEO?
The spam text and its links end up in the HTML of your own pages. Google’s spam policies name comment spam on blogs among the examples of user-generated spam and point site owners to tips on preventing abuse.
Marking links in comments
For links in comments and forum posts, Google recommends the ugc value of the rel attribute. It can be combined with nofollow. Contributors with a long record of good posts may be exempted if the site owner wants to reward them.
<a href="https://example.com/" rel="ugc nofollow">my blog</a>
Common measures
According to reports from blog platforms and blogging guides, these measures are common:
- approve comments before they appear
- use a spam filter or CAPTCHA
- block known spam email addresses
- remove the website URL field from the comment form
FAQ
Does nofollow stop comment spam? It labels the links. The spam posts still arrive, so moderation and filters are needed.
Sources
- Spam policies for Google web search (user-generated spam) – Google Search Centraldevelopers.google.com
- Qualify your outbound links to Google – Google Search Centraldevelopers.google.com
- How to recognize comment spam – Jetpack (secondary)jetpack.com
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