While movies tend to retain their original titles worldwide, with a bit of leeway in the translation, TV series and books translated in other languages often have titles that are far removed from the original title.
Should we allow the use of non-English titles, alongside the English title if/when we have it, on the site?
I'm thinking about the questions, but also about the tags and the wiki entries.
The site is English speaking all over so English should be used as much as possible. Tags should most certainly be in English. However, questions and tag wikis are fine to mention the original name of the work too though I’d lean towards using English first most of the time.
Tag names are important, because we can only put one name there (perhaps adding others as synonyms). We should use the English name there, because we're an English-language site. As for what kind of English: in general, network-wide consensus is to use US English for tag names, although I think (can't find the meta now) that there's some leeway for this if we're talking about a work of fiction originally published in British English like Harry Potter and the Philosopher's [Sorceror's] Stone.
A good tag wiki should include a lot of useful information about the book/film/whatever, and I think the name under which it was originally published counts. This might be helpful for someone who wants to look up about it or find translations into other languages. So mention the English title and also the original title, and also any other alternative English titles (since some books have multiple translations with differing titles).
There's a lot more leeway in what you're 'supposed' to put in a question body, since that's (to some extent) 'yours' whereas tags and tag wikis are for the whole site. I'd recommend including the English title, since that's the tag name and what a lot of site users might be most familiar with, but you're also free to include the original title or any other versions you want.
For me, it depends on what question I'm answering, and where the media originates. Since we are a site based on English, I always try to provide the English title, whether or not that was the original language. If a work originated in a non-English title, unless it's become more known under that title, I give the original title, followed by the English one, e.g.
Enthiran aka Robot in the United States, is likely the film you're looking for".
If the querent indicates they read the work in another language, I'll generally provide that title first, even if it wasn't the original language, e.g.
"Based upon you reading it in Spanish, I suspect you read La esclava de Gor, aka Slave Girl of Gor, by John Norman."
Just for the sake of completeness, I tend to do the same thing for title changes, using the title most likely to match up against what the querent was looking for, and then providing the original title.
