Flarum doesn't make any provisions (such as adding a field to identify content language for multilingualism, so this
Languages can be switched at the flick of a button.
isn't possible, but this
Additionally one can see posts from two languages together. That is, forum UI elements in one language but posts from two languages can be seen at the same time.
is quite possible. Install the right language packs and users will be able to see the UI in their preferred language. Content can be in any language, and you can set tags in multiple languages to help organize things ... but keeping the content organized by language will take a bit more effort on the part of users and moderators.
I believe it would be possible to create a Flarum extension to support the multilingualism seen in WBB. But as far as I know here are no plans to create such an extension.
