Sql Server Feature Or Bug?

Try this in sql server 2005:

select COALESCE(a1, char(254)) as c1 from

(select 'Z' as a1 union select 'Ya' as a1 union select 'Y' as a1 union select 'W' as a1) as b1

group by a1

with rollup order by c1

select COALESCE(a1, char(255)) as c1 from

(select 'Z' as a1 union select 'Ya' as a1 union select 'Y' as a1 union select 'W' as a1) as b1

group by a1

with rollup order by c1

 

The only difference is that the first one uses 254 and the second one uses 255. The first sorts like this:

W
Y
Ya
Z
þ

The second one sorts like this:

W
Y
ÿ
Ya
Z 

Is this expected behavior?