1. When viewing the details of a ticket, an agent can write a note instead of a reply. This is visible to any agent who looks at the ticket later, but is not sent to the user.
Agents receive an email or browser notification when a note is left on a ticket that is assigned to them or that they follow (depending on their notification settings).
2. An agent can @mention another agent within a note, to guarantee they will be notified regardless of their settings. This involves simply typing @ and then the start of the agent's name, then selecting the agent to mention from an auto-complete menu.
3. There is an agent IM system enabling real-time chat between agents. This is separate from the user chat system.