Congratulations on a great addon to Discourse.
I think there may be an issue with the latest version - or at least an incompatibility somewhere.
I upgraded QMP to version commit fe6ca1e this afternoon and users reported that their avatar was missing from the user menu (top right).
Here is a screenshot with the plugin enabled.
(The light grey square is due to mouse hover when I took the screenshot)
And here is one with the plugin disabled.
As you can see the avatar disappears when the QMP is enabled.
Examining the HTML of the #current-user element with the plugin disabled shows this.
<li id="current-user" class="header-dropdown-toggle current-user">
<a href="/u/saintbletch" data-auto-route="true" class="icon">
<div>
<img alt="" width="32" height="32" src="/user_avatar/www.sotonians.com/saintbletch/64/618_1.png" title="saintbletch" class="avatar">
</div>
</a>
</li>
And with the plugin enabled, you get this.
<li id="current-user" class="header-dropdown-toggle current-user">
<a href="/u/saintbletch" data-auto-route="true" class="icon">
<div>
</div>
</a>
</li>
Any ideas?