I should be able to whitelist a commenter across *all* of my Spaces

(User Story, Investigate , Priority: Medium, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Conversations, Moderation
Summary: That is, when I am moderating a comment and choose to whitelist someone, I should be able to whitelist them across all Spaces I own, not just this one.
Suggested by dsrtao.
This will be a nuisance to implement, since it has to bounce out to the UserSession, pick up all the Spaces, and fire the command out to all of them. But it's obviously something I want to be able to do -- if I know that Joe is a close friend who I trust, I don't want to have to individually whitelist him in each Space.
This obviously should only apply to Spaces that Joe has read access to.
Should I be able to do this for all Spaces I moderate, not just the ones I own? That might or might not be desireable; it's likely to be extremely challenging to implement, so we might limit this to ones I own.