Confirmed here
quote:
Originally posted by ahmetgns
Remember, when you choose not to display Plus! icons in Messenger windows, Plus! prompts you to restart Messenger for the changes to take effect. (By the way, MessengerDiscovery has the same limitation)
StuffPlug though doesn't force you to restart to hide or add its button.
I confirm the bug too
Windows XP Service Pack 2 (5.1.2600)
Windows Live Messenger 8.5.1018
Messenger Plus! Live 4.70.0.334