19. The system of claim 18 wherein: the user interface paradigm selection engine is configured to choose a subscriber-identity-module-aggregated user interface definition when the user interface type being displayed is a conversation user interface, even though the paradigm preference for messaging indicates a subscriber-identity-module-separated user interface paradigm.
18. The system of claim 16 wherein: the one or more stored user interface paradigm preferences comprise: a paradigm preference for calling; and a paradigm preference for messaging.