BuddyPress.org

@twistyfarmy – To disable notices, on your profile, navigate to “Messages > Notices” and disable them that way.

BP 1.7 introduced universal theme compatibility, but it appears your theme already has BP support, but did not tell BP this.  This is a possible reason why you see the sitewide notice at the top.

Follow the recommendation in this article:
BP Theme Authors: make sure your theme registers 'buddypress' support