'Today we are happy to announce the first step in advancing quantum resistance for the Signal Protocol: an upgrade to the X3DH specification which we are calling PQXDH. With this upgrade, we are adding a layer of protection against the threat of a quantum computer being built in the future that is powerful enough to break current encryption standards.'
Yes. He's still on the board. He stepped down because he had worked towards integration of a traceless and private crypto option for payments which critics felt made Signal more of a target for governments and to be used by criminal elements.
He was replaced as CEO by the previous co-founder of WhatsApp who used money from the sale to bankroll Signal.
But the idea Moxie isn't involved in crypto decisions for Signal is ludicrous. There's no way he's not actively being involved in protocol discussions.