[This is preliminary documentation and subject to change.]
Your authoring tool can store application-specific data as user comments in an event. For example, if your tool needs to identify which author has entered an event into the stream, it can store the user's name as a comment in the added event. The comment is stored as a microevent within the event.
To add a comment or custom data to an event, use the userdef keyword. The stream compiler objects provide several methods that enable you to set and edit user comments: EnhEvent.Attr, EnhEvent.Opcode, and EnhEvent.AttrCount. For more information about using these methods, see Adding User-Defined Comments to an Event.
The only limitation the stream compiler objects place on user-defined comments is that a comment cannot be followed by any other type of microevent, such as a file transmission or announcement. Custom comments are expected to be the last items in an event string, and as such, can only be followed by other custom comments.