Message
Encode "&" and "<" in plain text using hexadecimal character references.
Explanation
The specification has lacked clarity regarding whether HTML is permitted in elements other than an item's description, leading to wide variance in how aggregators treat character data in other elements. This makes it especially difficult for a publisher to determine how to encode the characters "<" and ">", which must be encoded in XML.
In elements that contain plain text, the form of encoding that works in the widest number of aggregators is using the hexadecimal character reference & to represent "&" and < to represent "<".
See Character Data in the RSS Advisory Board's Best Practices Profile (Proposed) for additional requirements and recommendations.
Solution
A publisher should encode "&" and "<" in plain text using hexadecimal character references. When encoding the ">" character, a publisher should use the hexadecimal reference >.
Not clear? Disagree?
You might be able to find help in one of these fine resources.
