I guess that's fair if you want to play it safe, but I don't agree that we should do something wrong because people are used to it that way. In Romanian “fata” can have 6 different meanings (some related) depending on how you put the diacritics: fata, fată, fața, față, făta, fâță. If you want your URLs to be meaningful and you care about people who don't use only English letters you should use all types of letters.