This site gives a detailed explanation:
http://www.flagsarenotlanguages.com/blog/
They provide a good visual aid for both the current setting and the place to click to change the language. I'd see removing this as a decrease in usability.
seems like sort of a nit-pick because for the most part the flags are a nice icon to quickly identify language, and as far as I can tell osu! is doing a good job of using flags to identify the right regional variant of language (English is British English, Spanish is not Latin American Spanish, China/Taiwan flags are used for simplified/traditional, ...). the region also isn't particularly important for osu!, it's just a visual aid like peppy says
the only alternative I can think to show the current locale without clicking is to just write the language but... 
idk this looks kinda silly to me to show at the top of every page. maybe I'm just not used to it
We can show the language code instead (pt-BR) as languages have different string lengths.
having to understand a set of language codes seems far less intuitive than just looking at a flag where the language is commonly spoken... are any of the osu! locales being misrepresented in some way by the flag?
The button displays the language code while the dropdown menu has code + full language name (or even just full language name). There is nothing here to remember/understand, same with flags. I think it's just the familiarity of a person's country and it's flag.
I get that people probably know the commonly known language in their country, thus having the same flag represented as the country and language, but that doesn't apply to knowing multiple languages, living in a country that doesn't have an official language, moving countries, etc.
Or just google the definition of a flag.
Crowdin also represents languages as flags. I'm either way if this was one of the reasons of keeping it as is.
are any of the osu! locales being misrepresented in some way by the flag?
Let's take a look at some of the largest /problems that osu!'s current flag system has with regards to the distinction between sovereign states and languages.
English (UK flag):
Spanish (Spanish flag):
French, Dutch, Portugese, etc.:
Literally everywhere:
This really doesn't need to be a problem, there are a plethora of different solutions that don't at all require compromising the cleanliness of the current design without adding locale text:
From a Flags are not languages case study:
So in conclusion, if you鈥檙e planning on implementing a dropdown language switcher, consider the following:
- always supplement your dropdown with links in the footer
- use a globe or similar icon to communicate translations to the user along with language labels
- flags don鈥檛 appear to aid nor hinder users compared to using icons/common UI patterns, but by using them you鈥檒l probably find yourself stumbling into several problems outlined elsewhere on this blog.
osu! seems to have a more multicultural and diverse playerbase than any other game I've ever seen, and it stands to reason that their languages should be respected. It's easy for speakers of majority European languages to take for granted our status as the "default" in so many circumstances, but it's very easy to alienate others.
everyone i've asked so far prefers flags, for the record. including all the team members that have had an opinion on this. we get that there are political issues and some discrepancies, but as a visual aid it helps in 99% of cases.
Of course鈥攊t is a matter of opinion in the end, but just keep in mind that a vast majority of the team members are from countries that have the "default" privilege in most cases. 馃槈
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everyone i've asked so far prefers flags, for the record. including all the team members that have had an opinion on this. we get that there are political issues and some discrepancies, but as a visual aid it helps in 99% of cases.