This plugin will integrate AJAX commenting feature into your WordPress Blog. It uses the powerful JavaScript Framework jQuery to handle AJAX requests and jQuery Validation plugin by bassitance.de to validate comment form on the client side.
<h4>Feature Summary</h4>
<ul>
<li>Enable AJAX Commenting</li>
<li>Client Side Form Validation</li>
<li>Easily rolls back if JS disabled</li>
<li>Easily configure custom styles for messages</li>
</ul>
<a href="http://webdeveloperplus.com/wordpress/new-wordpress-plugin-wdp-ajax-comments/" rel="nofollow ugc">See plugin page for more details</a>

WDP AJAX Comments

This plugin will enable AJAX comment posting on your WordPress blog.

Ramoonus

This plugin updates <a href="http://jquery.com/" rel="nofollow ugc">jQuery</a> to the latest official stable version, which is most likely not available within the latest stable release of WordPress. 
jQuery Migrate is also included for backwards compatibility.
No files are replaced, therefore deactivation of this plugin returns your site to it`s original state.
Since WordPress 5.6 includes an up-to-date version of jQuery 3, upgrading shouldn’t`t be necessary in most cases.
Warning
If you are not familiar with beta testing, bugfixing, javascript or running bleeding edge software it`s not recommended. 
I will not provide help on JavaScript and jQuery, only on plugin related issues (PHP)!
Reporting problems
Please post bug reports and request for help on <a href="https://wordpress.org/support/plugin/jquery-updater" rel="ugc">WordPress.org Support Forums</a>.
If you run into any bugs, turning this plugin off will fully deactivate everything.
Work in Progress
<ul>
<li>Options screen to enable/disable</li>
<li>Option to choose a specific jQuery version</li>
<li>Automatic cache flushing</li>
</ul>
For more information on the development visit the plugins <a href="https://github.com/Ramoonus/jQuery-Updater/issues" rel="nofollow ugc">GitHub</a>

jQuery Updater

Simple plugin

This plugin updates jQuery to the latest stable version on your website.

WDP AJAX Comments vs jQuery Updater