They are using Microdata format to semantically markup author (user) information:
ie, your name, title and photo.
[code=rich]<div class="messageUserInfo" itemscope itemtype="http://data-vocabulary.org/Person">
<div class="messageUserBlock">
<div class="avatarHolder">
<a class="avatar Av521m" itemprop="photo" data-avatarHtml="true">
<!-- Avatar -->
</a>
</div>
<h3 class="userText">
<a class="username" itemprop="name">Brogan</a>
<em class="userTitle" itemprop="title">Well-Known Member</em>
</h3>
</div>
</div>[/code]
You can read more about it over here: People - Google Webmaster Central.
(check the html source given under the 'Microdata' heading near the end of the page)
