Thread:Project:Support desk/Bad Url for Title with UTF/reply

I would decode the Unicode escape sequences; then it works for me:

http://en.wikipedia.org/w/api.php?action=parse&page=Gabriel_García_Márquez

or even

http://en.wikipedia.org/w/api.php?action=parse&page=Gabriel_Garc%C3%ADa_M%C3%A1rquez