MD: (6) How does the client measure packet loss? It's worth pointing out that there is no receiver packet loss detection mechanism in QUIC, so this has to be invented out of whole cloth. Reading between the lines both here and in the MC_INTEGRITY section, I think you have an implied requirement that servers MUST NOT skip packet numbers in the channel; if so, write that down.
MD: (6) How does the client measure packet loss? It's worth pointing out that there is no receiver packet loss detection mechanism in QUIC, so this has to be invented out of whole cloth. Reading between the lines both here and in the MC_INTEGRITY section, I think you have an implied requirement that servers MUST NOT skip packet numbers in the channel; if so, write that down.