Why SQL Server Ignores vaules in string concatenation when ORDER BY clause specified

Question

I have the following table

Created    Comment
2010/10/10 Text1 
2010/11/11 Text2
2010/12/12 Text3

I need gather all comments into the singl

Answer 1

Because you are relying on undocumented behaviour.

Microsoft say "The correct behavior for an aggregate concatenation query is undefined.". If the compute scalar moves to the wrong place in the plan then it just stops working!