As a mailing-list bound software professional, this is wonderful news. Maybe one day we will be free of software development on MLs.
As someone who formerly used to be in no-ML camp, I am proudly converted. Mailing Lists are decidedly democratic, and have least barrier to entry. It is also technically superior in providing unified interface to patches, communication, bug reports and everything adjacent. Compared to that any fancy service provides lock-in under thin veil of "friendly interface".
Now, there are strengths too. Like being archived easily & having threaded conversations integrated.