To manage complexity related to messages and comments about collaboratively edited electronic documents, an electronic document has associated activity data and comment data, where a type of activity data includes messages among users. Message data is stored in a stream of activity data in a format that is accessible both to communication applications outside of the electronic document, and to end user applications for editing the electronic document. The message data can include a document identifier, a user identifier for a sender and/or a receiver, and content of the message. A communication application, given a user identifier, can access document messages for that user, from a single electronic document or over multiple electronic documents. Further, the communication application can be notified when new document messages related to a user identifier are added to one or more electronic documents. Additionally, the end user application, given a document identifier, can access document messages associated with that document identifier for inclusion in the activity data for the document.