I think Flow should query the server every few seconds or minutes and show new messages on a page I opened, without me having to reload it.
(from merged task)
When a user posts a message on a Flow board and goes to the previous page, the message appears to be lost (page is not reloaded).
The same when a message is posted on a Topic and when you go back to the Board.
Also see this screencast.
Idem after posting a message: if post a message, go to an other page and then go back to the Flow board, the message you have posted is not visible.