It's very common use case that, while any agent is handling the chat, some other agent would like to guide or share any info with him/her. It's designed very awesome way in tawk.to. Any other agent can enter in chat and send messages which only agents can see. So, if any agent is not able to handle chat, someone can whisper replies to guide. And I'm sure everyone face such situations. Users don't want to talk with multiple agents in single chat definitely.