19.431 script:event-name - poor wording of namespace requirement -see description

"Since the available events, their names and their meanings are implementation and script language dependent, the name should begin with a namespace prefix followed by a ":" (COLON, U+003A), so that the corresponding namespace together with the event name can be used to identify the semantic of the event."

Don't have to give rationale. Just state the rule.

Thus:

Event names should begin with a namespace prefix followed by a ":" (COLON, U+003A).

Note: The use of namespaces with event names may help consumers with the semantic of events.