While someone makes a change to a page on his computer, other people may be viewing that very same page. It would be neat, using AJAX, for the user viewing the same page to see the update once the first user saves his changes.

Such a feature would consume a lot of traffic and so we may want to do that only in a few cases (i.e. front page, pages considered live.) With HTTP2 we can actually keep a connection open, so it uses a lot of connections but not so much traffic (i.e. we can switch from a Poll system to a Push system so if someone is on page A and page B gets edited, not much happens with this feature using HTTP2. With a Pull, that other user would continue to check for changes to page A every now and then... but we'd save that one socket.)

This is very similar to getting comments posted in real-time (as on Facebook) but with actual pages. The process would be the same since a page or a comment is the same type of objects in the database.

See: Comment feature

See: AJAX feature (Inline Editing) [core]

See: Chat feature