For unmodified links Nofollow Case by Case works like a (do)follow plugin for WordPress. It simply removes rel=”nofollow” from your comment links.
Whenever you get the feeling that one of your comment links might be able to harm your own website reputation, if you think about SEO and found a link that looks a bit like spam but should not be deleted, you can replace nofollow to every single comment link at any time. If you want to replace nofollow for a link like that you simply add /dontfollow at the end of the link. You can do this for author links in comments as well as for the links you find in the text.
<h4>This is what the plugin will do automatically:</h4>
1. Clean up some code: 
It tries to remove all variants of rel=”nofollow”, target=”blank” and rel=”external” from comment author links and other links in comments first. A link will become a “real link” no matter if it is a pingback, a trackback or a “real comment”.
2. Fix semantical incorrectness: 
The plugin now applies rel=”external” – but ONLY for external links!
3. jQuery functions of Nofollow Case by Case:
a) The plugin detects rel=”external” in comments and opens those links in a new window. 
No need for target=”_blank” which would not validate in XMTML. jQuery replacement does.
b) The plugin tries to correct author urls that could not be fully replaced before. 
This has something to do with template development. Find more information on this within the FAQ.
<h4>Add on</h4>
You can try this <a href="https://wordpress.org/extend/plugins/nfcbc-seo-plugin-add-on/" title="NFCBC SEO Plugin Add-on" rel="ugc">NFCBC SEO Plugin ADD-on</a> for easier comment management. The plugin is an old one using javascript but still works. I currently do not have the time to rebuild it. A new version should later support Ajax and nonces and on the other hand will not support old versions of WordPress anymore.
<h4>Alternative Tool</h4>
<a href="https://wordpress.org/extend/plugins/nfcbc-seo-light/" title="NFCBC SEO Light" rel="ugc">NFCBC SEO Light</a> could be used alternatively. It suggests “follow” or “nofollow” or “no link” automatically, depending on comments length. This plugin might be updated soon. I personally prefer Nofollow Case by Case.
<h4>Need more information?</h4>
I have updated the <a href="https://wordpress.org/extend/plugins/nofollow-case-by-case/faq/" title="FAQ for Nofollow Case by Case" rel="ugc">FAQ for Nofollow Case by Case</a> and the German description can be found at the old place as well:
<ul>
<li><a href="http://www.fob-marketing.de/marketing-seo-blog/wordpress-nofollow-seo-plugin-nofollow-case-by-case.html" title="Nofollow Case by Case SEO Plugin" rel="nofollow ugc">Deutsche Plugin-Beschreibung auf fob-marketing.de</a></li>
<li><a href="http://www.fob-marketing.de/marketing-seo-blog/antworten-zu-nofollow-case-by-case-und-relexternal-nofollow.html" title="FAQ bei fob marketing" rel="nofollow ugc">Deutsche FAQ auf fob-marketing.de</a></li>
</ul>
<h3>Contact</h3>
For further information please send me an <a href="http://www.fob-marketing.de/fob/ueber-fob-marketing/fob-marketing-kontakt/" title="Send an email to Oliver Bockelmann" rel="nofollow ugc">email</a>.

Nofollow Case by Case

"Dofollow" but Nofollow Case by Case allows you to selectively apply nofollow to your comments as well.

NFCBC SEO Light – The light version of <a href="http://www.fob-marketing.de/marketing-seo-blog/wordpress-nofollow-seo-plugin-nofollow-case-by-case.html" title="Nofollow Case by Case" rel="nofollow ugc">Nofollow Case by Case</a>?
You might have heard rumours about pagerank sculpting (old school -> new school). 
You might have heard about follow and nofollow links. 
You might not love the idea of blocking every single comment link. 
You might not love the idea of moderating every single comment link.
How about voting with good links for great comments only?
Supported options of NFCBC SEO Light:
<ul>
<li>No link for very small comments (default: 50 characters). </li>
<li>Nofollow link for small comments (default: 170 characters). </li>
<li>Follow links for large comments, pings and trackback links. </li>
</ul>
Default values can be replaced for every single link.
Author link exeptions can be made like this:
Add /dontfollow to the author link to get a nofollow link. 
Add /thisfollow to get a follow link. 
Add /nolink to show the author name without a link.
<h3>more info</h3>
Please visit [fob marketing](http://www.fob-marketing.de/marketing-seo-blog/ fob marketing) 
for more information.
This program is distributed in the hope that it will be useful, but 
WITHOUT ANY WARRANTY; without even the implied warranty of 
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

NFCBC SEO Light

NFCBC SEO Light - The light version of [Nofollow Case by Case](http://www.fob-marketing.de/marketing-seo-blog/wordpress-nofollow-seo-plugin-nofollow-c …

Nofollow Case by Case vs NFCBC SEO Light