In the Atom feed, any HTML special characters need to be double-encoded.
For example, this item appeared in an Atom feed recently: <kbd> elements are way intrusive
In the Atom feed the title was encoded as:
<title type="html"><kbd> elements are way intrusive</title>
This actually needs to be double-encoded, i.e.:
<title type="html">&lt;kbd&gt; elements are way intrusive</title>
On Google Reader and on Firefox, it thought an actual kbd
tag was there, and in both cases it was stripped out (so the title actually read "elements are way intrusive").