Robert Sayre wrote:
Software written to conform to this version of the specification will not be able to process such markup correctly and, in fact, will not be able to distinguish it from markup error.
Please replace that sentence with something reemphasizing the MustIgnore rule.
Stating that nobody else is allowed to use the Atom namespace, coupled with a statement that everybody must ignore elements that they don't understand paves the way for future IETF spec authors to safely add optional elements in a backwards compatible manner.
- Sam Ruby
