David Garcia

This plugin removes the replytocom parameter that wordpress uses in threaded comments. Replaces them with a data-replytocom and later rebuild the href via an ajax call. This avoids duplicated content and favor SEO optimizations.
Visit the <a href="http://www.seocom.es/" rel="nofollow ugc">Seocom website</a> for more information about SEO or WPO optimization

ReplyToCom Ajaxify

Removes the ReplyToCom parameter from the comments querystring. This action favor the SEO optimizations.

ClaytonL

Hate duplicate content? Hate wasting server resources?
Replytocom Controller gives you the option to remove “?replytocom” from comment urls and optionally redirect visitors & bots who try to use it anyway to a destination of your choice.
For those concerned about duplicate content for SEO purposes, the benefits should be obvious.
If you want to speed up your WordPress server, the redirection will let you stop wasting resources serving up the same page over and over again to a crawler bot. Even worse, pages with a question mark in the url aren’t typically cached by caching plugins like WP Super Cache. That means that those bot crawls are eating up way more resources then a normal url would. Now you can send them to a cached copy of that page, a less resource intensive page, or any other url.
Of course, the cost of all this is that visitors can’t have JavaScript turned off if they want to leave replies in threaded comments.
Borrows code from: 
* https://wordpress.org/extend/plugins/all-in-one-seo-pack/ 
* https://wordpress.org/extend/plugins/replytocom-redirector/

Replytocom Controller

Replytocom Controller lets remove "?replytocom" from comment reply urls and redirect bots who try to use it anyway.

ReplyToCom Ajaxify vs Replytocom Controller