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.

Ariagle

Not everyone wants to leave a comment, and you don’t know who have read your post without feedback. WP-Clap helps you make your visitors leave simple feedback without type a comment.
WP-Clap will creat a clap area after your post. Just like the comment area, your readers can clap for your post after reading, but they do not need to type anything. You can also use our function in your homepage to show how many claps the posts have, just like how many comments there are.
并不是每个人都会留言，日志冷场现象经常出现。WP-Clap插件允许你的读者在浏览日志后能轻松简单地留下路过的印记，减少冷场现象。
Features:
<ul>
<li>AJAX Clapping</li>
<li>Avatar suppor</li>
<li>Clapper details(name, email, url, date)</li>
<li>Image clap link</li>
<li>Custom clap text</li>
<li>Custom HTML notice</li>
<li>Auto insert into post and excerpt</li>
</ul>
equires Version:
I don’t know whether WP-Clap can work at WP 2.5 or lower, but you can have a try.
Supported Languages:
<ul>
<li>US English/en_US (default)</li>
<li>简体中文/zh_CN (translate by <a href="http://blog.lolily.com/" rel="nofollow ugc">Ariagle</a>)</li>
<li>日本語/ja_JP (translate by <a href="http://xiaolife.com/" rel="nofollow ugc">晓晓</a>)</li>
<li>Dutch/nl_NL (translate by <a href="http://blog.bokhorst.biz/" rel="nofollow ugc">Marcel</a>)</li>
</ul>

WP-Clap

Not everyone wants to leave a comment, and you don't know who have read your post without feedback. WP-Clap helps you make your visitors leave si …

Comment Load More vs WP-Clap