Clarify when not to update atom:updated
The second sentence ("not all modifications...") is a bit vague and conceivably contradicts the first (which implies "only some", second implies "most"). NB This is not an attempt to change the meaning.
Change second sentence of:
The "atom:updated" element is a Date construct indicating the most
recent instant in time when an entry or feed was modified in a way the producer considers significant. Therefore, not all modifications necessarily result in a changed atom:updated value.
Therefore, other modifications SHOULD NOT result in a changed atom:updated value.