Languages should never be represented with a national flag.
- A country with a history of British colonization may still use English as their official language, and using the Union Jack to denote their official language could be offensive.
- A country may have more than one language in common use, and using the national flag to refer to only one language would mean ignoring the other communities.
- Using the German national flag to refer to the German language would imply that the Federal Republic of Germany has some kind of language authority, while other German-speaking countries (Austria, Switzterland, etc.) don't.
- Using national flags is not a scalable approach; Some languages don't have a corresponding flag at all.
Most languages are not one-to-one correspondence with a state. If you need a good way to identify languages, please use the name of them just like vuejs.org does so.
Special thanks to @xtendo-org, for bringing up this problem.