Patch 183.0 added a new chat-variant. Called “Local-Chat” it allows you to chat with everyone in the proximity, but excludes the rest of the server. That could for example be useful for people who end up having to ask for help, but don’t want to advertise their precarious situation to everyone on the server.
You can access it with the “Insert”-key. That will change the “Global”-Label left of the chat input to “Local”. Local Chat is distinguished by the suffix “(LOCAL)” in the chat-window.