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.

Marc Tönsing

lefalque

Adds a link next to the reply link below each comment, which allows visitors to flag comments as inappropriate. 
A sub page to comments in admin is added, where an administrator may review all the flagged comments and decide 
if they should be removed or not.
Admins or logged-in users with comment moderation permissions are able trash or replace comments with 
one click in the frontend. This action can not be undone. A “trash” link will appear bellow all comments. 
Don’t worry: You can untrash them if until you reload. You are also able to replace the comment text with a custom 
text which can be set in the settings.
<h4>Features</h4>
<ul>
<li>Ability for visitors to report comments they find offensive.</li>
<li>Once a flagged comment has been deemed ok, it wont be able to be flagged again.</li>
<li>Flagging is done via ajax for smoother experience for the visitors.</li>
<li>Decide whether all visitors or only logged in users can report comments.</li>
<li>Trashing and Replacing with ajax in the frontend for faster moderation.</li>
<li>Fully localized. Comes with English and German translations.</li>
</ul>

MarcTV Moderate Comments

Grants visitors the ability to report inappropriate comments and admins to replace and trash them in the frontend.

Comment Load More vs MarcTV Moderate Comments