Actually, the shoutbox in IIP 5.3 only updates if the input box is unfocused. Every time you activate the input box, the counter is stopped and it is restarted when inactivating it.
I tend to use it when I'm reading the backlog so that it won't update while I'm reading. Just click in the input box to focus it, and then I go to the top and read the whole thing without being disturbed by refreshes. Really nice. =]
