I'm ok with locking in 4 and 8.

I want to agree to locking in 1, multi-device feeds. However, I'm not clear if this is going to be implemented as sameAs -- which I'm concerned is a security risk, as someone could pretend to be my feed with this strategy.

I want to see multi-device feeds implemented as subkeys using libsodium -- similar to how Bitcoin issues subkeys for receive addresses. Is this @matt's approach? If this is his approach, then I can support 1. If not, I cannot.

I'm currently making up my mind on the 4th proposal.