using stuff for fullname when task is same for two person even though fullname is not separating with comma

;WITH temp as 
(
	SELECT DISTINCT  
		u.TM_UserID
		task_name
	FROM 
		project  
		JOIN task 
		   ON project.project_id=task.project_id
		JOIN timesheet  
		   ON timesheet.task_id=task.task_id
		JOIN Team 
		   ON project.project_id = Team.project_id
		JOIN TM_user u 
		   ON u.TM_userID=timesheet.user_id
	WHERE u.Is_Active=1 
		AND u.report_to=13 
		AND worked_dte BETWEEN '2014-03-18' AND '2014-03-21'
)
select 
	task_name 
    ,STUFF(
			(
				SELECT ', ' + U1.FullName
				from TM_user 
				INNER JOIN temp ON temp.task_name = temptbl.task_name
				FOR XML PATH ('')
		    ), 
		    1,
		    2,
		    ''
		  ) FullName
from temp temptbl
Group BY task_name