Patch 2.6.6a was released overnight…
https://us.diablo3.com/en/game/patch-notes/2-6-6a
Several bugs regarding Battlenet Services and Localization have been addressed
Hopefully this should see an end to the issues regarding clan chat / community chat / inviting players into games / having to leave party to swap heroes / clan members showing as level 0 / friends list showing players as offline even though they’re actually online / broadcasts being sent and then immediately removed, and so on.
[ EDIT ]
Seems like it didn’t fix it after all…
[ EDIT 2 ]
Update from Blizzard on US forums…