If you want someone to join your chat, all they have to do is type "/join ". In Legacy of the Void, we’ve made chat channels easier to join by added the ‘/join’ command.
Take a look below for more details on the changes included in patch 3.00. The menus have also had a visual overhaul. The new system provides persistent chat and tweaked how players connect to games in the Arcade mode. As mentioned in the video, creating a more social experience was a key design principle the developer kept in mind when reworking the UI.