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Something else is going on here. A valid server never returns an URL with non-ASCII chars. Your test server does the right thing, too:
$ LC_ALL=C wget http://www.libon.it/libon/search/isbn/3499155443
--2013年07月19日 11:01:54-- http://www.libon.it/libon/search/isbn/3499155443
Resolving www.libon.it (www.libon.it)... 83.103.59.131
Connecting to www.libon.it (www.libon.it)|83.103.59.131|:80... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: http://www.libon.it/ricerca/7818684/3499155443/dettaglio/3102314/Onkel-Oswald-und-der-Sudan-K%C3%A4fer/order/date_desc [following]
Incomplete or invalid multibyte sequence encountered
--2013年07月19日 11:01:54-- http://www.libon.it/ricerca/7818684/3499155443/dettaglio/3102314/Onkel-Oswald-und-der-Sudan-K%C3%A4fer/order/date_desc
Reusing existing connection to www.libon.it:80.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
I have digged through the code. Now I think that I know what's going on here. The header parsing code unquotes and converts the Location header. The code in the 302 handler doesn't compensate and therefore fails.
Here is a patch that corrects the code in the 302 function.