In online pseudonym parties, perhaps an off-state set of keys could be used both for encrypting the video stream, and for the selfie-videos that "commit" each person to a pseudonym party.
That would remove the trace between the on-state identities and off-state signatures, two mirror universes more or less but with no cryptographic links.
The handshake in the communication channels could be with on-state keys, and off-state keys are then exchanged, that authenticate and encrypt all video data, still provable to the people who are interacting with one another, tough without any on-state proof of any subjective data.