BuddyPress.org

as in the autolinking and email notification during an activity update? You’ll need to remove all the filter hooks and the subnav for the mentions tab.

bunch of filters on bp_activity_at_name_filter, bp_activity_at_message_notification, groups_at_message_notification

bp_core_remove_subnav_item($bp->activity->slug, ‘mentions’)

(though i’m not if someone has created a plugin for it)