Originally you had a view of notes (formerly messages) where you only saw the initial text of each note, and from there you could jump to the full view of each message, where you saw the additional text and the comments (like in a blog, where you have a list of posts on the main page but when you go to the page for a specific post you see the entire text and you can leave comments).
Currently the additional text has no use, but it may be used again in the future for the RSS or mail notifications, where only the initial text would be shown. We have no specific plans for it yet though.
