You could use a delimiter field to add whatever text you want to every uses profile.

As for modules simply use whatever module you'd like and place it on profiles. Believe we're using CB Content and loading in custom jQuery/CSS to make it the sticky note.

If you need users to be able to reply you could use a Joomla article and display it on your frontpage then ensure you've a comment extension installed so they can comment. Alternative is to use Kunena and simply make a forum post.