It's not a bug.
The syntax you are using is never reliable to get string concatenation in T-SQL.
BTW, Order By 1 in your first sample, is not inequivalent to Order By seq... It is equal to
order by @comma_Delimited + k + ','
_____________________________________________
"The only true wisdom is in knowing you know nothing"
"O skol'ko nam otkrytiy chudnyh prevnosit microsofta duh!":-D
(So many miracle inventions provided by MS to us...)
How to post your question to get the best and quick help[/url]