Marc Tönsing

Ipstenu (Mika Epstein)

This plugin displays the most basic of quicktag buttons on your comment forms, using the Quicktag API built into WordPress (as of 3.3). No jQuery needed.
Contribute on <a href="https://github.com/mtoensing/marctv-quicktags" rel="nofollow ugc">GitHub</a>.

Simple Comment Quicktags

Simple and clean

Make commenting easier with bold, italic, add link and quote buttons on top of the form.

Jesper Johansen (jayjdk)

This plugin, Jayj Quicktag, allows you easily to add custom Quicktags to the post, page, or a custom editor.
It adds a settings page where you can add all the Quicktags you want (see Screenshots)
It supports both import and export of your Quicktags so you easily can add them to another WordPress install.

Jayj Quicktag

Allows you easily to add custom Quicktags to the post editor.

Simple Comment Quicktags vs Jayj Quicktag