The following entry has been added to the addon compatibility alias and may explain what's going on with the chat system:
Lua Code:
-- CHAT_SYSTEM refactor
-- Many of the internals/method calls have changed in chat system to support multiple chat systems at once.
-- This will preserve compatibility with addons that add messages to chat using CHAT_SYSTEM:AddMessage(), but more complex chat addons may need rewrites.
CHAT_SYSTEM = KEYBOARD_CHAT_SYSTEM
function CHAT_SYSTEM:AddMessage(messageText)
return CHAT_ROUTER:AddSystemMessage(messageText)
end