"%s" vs unicode

[Robin Becker]

In article <m3u1gkwvui.fsf at mira.informatik.hu-berlin.de>, Martin v.
Löwis <martin at v.loewis.de> writes
>Robin Becker <robin at jessikat.fsnet.co.uk> writes:
>
>> That was considered harmful (although I disagreed) so why is this
>> implicit conversion allowed? 
>
>It follows the general principle that, when combining byte strings and
>Unicode strings, the byte string will be converted to Unicode, not
>vice versa.
>
>Regards,
>Martin
>
but the general principal here is that %s converts things to strings.
What is general about breaking this? 
-- 
Robin Becker