This wouldn't solve your original problem since UTF8 also popular with Japanese, so just adding Shift-JIS isn't enough, so it comes down to the same basic thing: to support Japanese, you have to do some extra work to get and use extra info about a language, which is also possible within UTF8 counter to your initial broad claim of the opposite
> This wouldn't solve your original problem since UTF8 also popular with Japanese
Only among people who don't care. Implementing encoding support means your app supports a way to display Japanese properly. If you want to add more ways to display Japanese properly, go ahead, but that's supererogatory, whereas UTF8-only apps don't have a way to display Japanese properly at all.
> to support Japanese, you have to do some extra work to get and use extra info about a language, which is also possible within UTF8
It's not. There's some imaginary theorycrafted way in which it might notionally be possible within UTF-8, but not one UTF-8-only app has ever actually implemented support for displaying Japanese properly. The only approach to displaying Japanese properly that has ever actually been implemented in reality is to support multiple encodings (or to support only a Japanese encoding, but that has obvious downsides), and if you make your app encoding-aware then that's enough, you don't have to do anything else to be able to display Japanese properly for people who care about displaying Japanese properly (it's always possible for an app maker to go above and beyond, but I'm sure you'll agree the big difference is between an app that has a way to display proper Japanese at all and one that does not).
