Favorites
A member is favorited from their profile. They aren't notified, and never shown who has favorited them.
The Feed's Favorites tab carries their activity: the tasks they post, are booked for, and complete, plus reviews. When inviting members to a task, favorites are listed first.
The full list of favorites is on the member's own profile; each row shows how many tasks were completed together, and a favorite can be removed there.