tempranova

This is a simple plugin that uses AJAX to load comments, converting the “Newer/Older Comments” button into a button that loads more comments instantly.
This plugin also paginates nested replies. You can customize styling in whatever way you choose.
Using Settings > Comment Load More, user can set desired pagination (currently both comments and replies have the same number).

Comment Load More

This plugin allows you to load more comments instantly via a button push (AJAX), instead of pagination that reloads the page.

Vladimir Prelovac

WP Wall is a “Wall” widget that appears in your blog’s sidebar acting as a cool shoutbox for your visitors.
The comment will appear in the sidebar immediately, without reloading the page.
All comments are internally handled by WordPress so that means you have normal comment moderation, SPAM protection and new comment notification.
WP Wall is fully customizable with a CSS file and included graphics.
WP Wall features: 
* Global commenting “Wall” 
* Comments are handled entirely by WordPress 
* RSS Feed for the Wall 
* Smilies 
* Instant delete for admin 
* Option to display HTML and make links clickable 
* Navigation through pages 
* Interactive Wall: It can automatically refresh turning into a chat
Plugin by Vladimir Prelovac. Also check out <a href="https://managewp.com" rel="nofollow ugc">ManageWP</a>.
<h3>License</h3>
This file is part of WP Wall.
WP Wall is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
WP Wall 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. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with WP Wall. If not, see <a href="http://www.gnu.org/licenses/" rel="nofollow ugc">http://www.gnu.org/licenses/</a>.

WP Wall

"Wall" widget that appears in your blog's sidebar acting as a cool shoutbox for your visitors.

Comment Load More vs WP Wall