A thoughtful and interesting assessment:
Recent studies on notification timing have highlighted four types of solutions to manage user interruptions: "immediate, negotiated, mediated, and scheduled". Interruptions can be delivered at the soonest (immediate), or the person has explicit control over when they will handle the interruption (negotiation). A third party system may also dynamically decide when best to interrupt the user (mediated), or always hold all interruptions and deliver them at a predefined time (scheduled). In most situations negotiation is said to be the best choice. But I believe adding feedback to presence will require exploring dynamic combinations of negotiation and mediation.