Good question.

We're participating on the periphery of the MLS discussions, mainly to try to encourage the MLS team to consider and support decentralised use cases.

At the moment there's a temptation to go for a simpler approach which assumes there's a centralised sequencing server which solves all the races you otherwise get (and which have plagued us in Matrix whilst implementing Megolm). However, assuming a centralised focal point for each group conversation kills the whole point of decentralisation, so we're trying to ensure it's not designed out.

See https://mailarchive.ietf.org/arch/msg/mls/MnLJkbJ_Mwe8Oz0Ll6... for the gory details.

Has Matrix considered developing a DMLS (D for decentralized use cases) specification for submission to IETF?

We may have to go down that path if MLS ends up being decentralisation unfriendly.