Some people want more than one person assigned to a task, whereas others firmly believe only one person should own the responsibility for a single task.
Since people from these two walks of life tend to feel adamant about their preferences, we decided to let you make the choice.
Only one person can be assigned to a task. If you select another person, then the assignee for the task will change immediately.
One or more people can be assigned to tasks. When you select people, they'll be added to task assignees. Simply click people again to unselect them, or you can use the 'Reassign' feature to instantly remove current assignees and reassign to only one person.
How do I change assignees settings for Spaces? Simply go to your Space Settings page, and tick (or untick) the box for 'Allow multiple assignees'.