I have a problem with Comma Seperated values in the Sql Query

The Query Goes like this

DECLARE @dd TABLE (Username VARCHAR(250), WorkArea VARCHAR(50), Scope VARCHAR(50), Quality INT)
insert into @dd (Username ,WorkArea ,Scope ,Quality) select QAResource,WorkArea,ProjectScope ,quality from[PMT] .dbo.QADetailsnew
insert into @dd (Username ,WorkArea ,Scope ,Quality)select a.resources,a.work_area,a.scope, a.Quality   from [workalloc] .[dbo] .work a
 
;WITH UserTotals AS
(
        -- initial values
 
                SELECT LEFT(Username, CHARINDEX(',', Username )-1) AS SingleUser, Quality, RIGHT(Username, LEN(Username) - CHARINDEX(',', Username)) AS Remainder
                FROM @dd
                WHERE CHARINDEX(',', Username)>0
                union all
                select Username as SingleUser,Quality, NULL as Remainder
                FROM @dd
                WHERE CHARINDEX(',',Username )=0
               
        -- here starts recursive part
                UNION ALL
                SELECT LEFT(Remainder, CHARINDEX(',', Remainder)-1) AS SingleUser, Quality, RIGHT(Remainder, LEN(Remainder) - CHARINDEX(',', Remainder)) AS Remainder
                FROM UserTotals
                WHERE CHARINDEX(',', Remainder)>0
                UNION ALL
                SELECT Remainder AS SingleUser, Quality, NULL AS Remainder
                FROM UserTotals
                WHERE CHARINDEX(',', Remainder)=0
)
select distinct(SingleUser),(sum(Quality)/COUNT(SingleUser)) as QualityPercentage, 100-sum(Quality)/COUNT(SingleUser ) as ErrorPercentage
from UserTotals
group by SingleUser

Username      Quality%
aa,bb,cc      100
aa            99

SingleUser            Quality%
aa                    99 
bb                    100
cc                    100

Username                Quality%
bb,aa,cc                100
aa                      99

SingleUser              Quality%
aa                      100
bb                      100
cc                      100
aa                      99