As a default behavior, WordPress will automatically set all URLs in post comments to be rel=”nofollow”. This is one way of reducing spam submissions, given that search engines may not give any value to outbound links which have this markup. If it has no SEO value, there’s little incentive for spam comments.
There are occasions where you’d like to allow comments to be rel=”dofollow”, particularly when the comments are from valuable users or regular authors or contributors. In these cases, you’d like the ability to either manually set the links dofollow, or automatically set them, based on the valuable commenter email address - a whitelist approach.
Install the DoFollow Case by Case plugin using our How to Install Plugins procedure: 1)https://wordpress.org/plugins/dofollow-case-by-case/
Once the plugin is installed and activated, you can specify a whitelist of allowed emails that comments will be dofollow enabled.
Settings -> DoFollow
Or, you can set post comments dofollow one by one from within the post / comments section of the WordPress admin area. There are several different items, like author, URL and comment content where you can specify if links are to be dofollow, allowing you to have some, all or none (default) as dofollow.
Note: As with many plugins offering custom behaviors, it’s possible that this won’t work well with certain other themes and plugins. Try it, check a current comment link for a rel=nofollow or rel=nofollow,external, then mark that comment as dofollow using the plugin and reload/recheck the comment to confirm it is no longer nofollow. (You may have to clear browser cache and force a flush cache of WordPress or other caching mechanisms on the web hosting in order to see the latest updated version of the post and comment.).