I think the majority of manhua an manhwa (chinese and korean) have the main title in english because hardly anyone among your average western manga readers knows how to read these (as opposed to the old tradition of generating otaku interested in learning at least basic japanese).
AFAIK in case of manga, more groups have preference to rely on the translated english title in case of short stories and oneshots, and lean towards japanese ones otherwise. I think the former used to be true in case of yuri/yaoi too, but I'm not 100% sure of that and don't know the current situation either. There is also the preference of romaji because of it being more error-proof and usually what's on baka, but it's not a hard rule and the main title shouldn't affect the searchability of a work as long as both the english and the romaji or kanji titles are present (then there are exceptions like obscure oneshots the translator never gave the original name of and even on baka no one bothered to find the japanese name of theirs).
Then there are some non-asian, non-japanese comics here too, and with self-published works the authors are free to choose whatever title they want for their comic.
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two threads about it (the latter is just an old thread with users discussing japanese vs english preferences) :
https://vatoto.com/forums/topic/26439-what-is-the-official-policy-regarding-series-metadata/
http://vatoto.com/forums/topic/20055-manga-titles-japanese-or-english/
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and small correction to what daktyl said: alt title and genre edits are available directly on the comic page (blue pencil icon), everything else is behind the edit button (but you seem to be already aware of it)
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fake edit:
about duke's daughter, seems to be a case of a small edit war over 2 years, with various uploaders and a few random users changing it to whatever title they prefer, and with the initially used one being in japanese.
not necessarily the case here, but there are always some users that want to align everything to one spectrum and have a habit of changing the main titles if they seem out of place to them (although I think the romaji preference is still relatively more common there).
ah, it reminds me I forgot to lock the voting thread I started for some comic to let the readers pick the title they want themselves .-. this comic could use one too I guess...
the duplicate comic you're right in that someone forgot to search and/or didn't know how to edit and just added a new entry with a bad title to get it through (you get an error if you try to add something with an exact same title as something already in the database, hence some shorter titles get the author's name added in parentheses, and duplicates may have misspellings in them). duplicates are against the rules though and users are encouraged to report these in the dedicated thread in the quality assurance subforum
Edited by OMGWTFBBQPONIES, 10 October 2017 - 07:38 AM.