I have worked on sites that use english URLs for all languages. It isn't the best user experience but it doesn't appear to hurt rankings. Or, I should say these sites have ranked well despite this, although it is hard for me to know if they could have ranked better.
The reasons we went with english urls:
1) Urls are the same across all languages, which makes directing users to the same content across languages very easy.
2) Our site is translated. Translating urls would be possible but could be problematic. Specifically, urls should not be editable as easily as other translations. When a translation change IS made for a url, it would need to have redirects put in place to handle the old version.
3) When we localized our site (8 years ago) non-ASCII urls were not well supported by all browsers. I believe browsers support this better today, but I'd investigate this first.
non-ASCII urls were not well supported by all browsers
Display of the URL is secondary. The big problem is getting there in the first place. All you have to do is run into one server that thinks %E1%90%80 began life as three one-bit characters instead of one three-bit character, and your whole URL flies down the tubes.
Your page titles can be in any script you like, so long as you remember to specify a file encoding before the <title> tag. And that's what people see.
@deadsea Thank you so much for giving your personal experience with URLs translation. I very much appreciate.
@lucy24, Oh man, your answers are always complicated but insightful indeed. So that It takes me a lot of time to understand what you actually meant to say.
You guys in this forum are truly experts. I wish I could become like you all.
I asked this question because when a visitor is using the Japanese version of Google and typing something in Japanese in Google search, either a page with Japanese words in the URL will show up/preferred or a page with English words in the URL?
Because, I read that URL structure also plays an important role in top ranking. I mean using main keywords in the URL. In that case, would it be good to use English key queries in URL for page with Japanese content?
Wouldn't that make the SE's confused and degrade my page?