. "The Server MUST store the message in accordance to its QoS properties and ensure onward delivery to applicable subscribers [MQTT-4.3.3-2]."
This requirement is a duplicate of MQTT-4.3.2.2. And if it is not due to a different context, then this context should be part of the requirement. Again, more generally tagged normative statements should be made "self-explanatory" and as little dependent from their context as possible (must make sense when taken out of context).