Hinaloe

This plugin allow your site’s comment form makes ajax — non move/reload when user (including both subscriber, normal viewer, and admins too) post comment!
Most themes supports this plugin, but if your theme’s <code>class_form</code> have not <code>comment-form</code>, this plugin non supported.
And this plugin only can use for Pure WordPress Comment form. 
so, its not able to be used with like Jetpack comment form and other original/outside comment system/form.
Feature
<ul>
<li>post comment with ajax</li>
<li>Lite — this plugin only using a little of jQuery feature to modify DOM, and very tiny js & PHP code.</li>
</ul>
Require
You have to install <a href="https://wordpress.org/plugins/rest-api/" rel="ugc">WP REST API v2</a> to use this plugin if your site is running on WP 4.4-4.6.

ajax Post Comment

Post comment form on frontend tobe ajax using WP REST API Version.2

10up

Taylor Lovett

If you are publishing content and have users/websites digesting your content, you may have been faced with the problem: how do I get updates to users immediately? In the past users/websites have subscribed to feeds or used techniques like “polling” to constantly ping your site for new content. Both these techniques are cumbersome and old fashioned. JSON REST API Subscriptions creates new API endpoints to allow people to subscribe to new content, content updates, and content deletes across general post types as well as single pieces of content.
Requires <a href="https://wordpress.org/plugins/rest-api/" rel="ugc">JSON REST API 2.0beta12+</a>.
For details on the plugin and extended usage/installation documentation, please visit <a href="http://github.com/tlovett1/json-rest-api-subscriptions" rel="nofollow ugc">Github</a>.
<h3>Configuring and Using the Plugin</h3>
Please refer to <a href="http://github.com/tlovett1/json-rest-api-subscriptions" rel="nofollow ugc">Github</a> for detailed configuration instructions.
<h3>Support</h3>
For full documentation, questions, feature requests, and support concerning JSON REST API Subscriptions, please refer to <a href="http://github.com/tlovett1/json-rest-api-subscriptions" rel="nofollow ugc">Github</a>.

JSON REST API Subscriptions

Enable subscriptions to posts, pages, and custom post types. Users can securely subscribe via simple API routes to created/updated/deleted content.

ajax Post Comment vs JSON REST API Subscriptions