languageCode is only used to set the languageCode field in the RSS feeds.
Currently Hugo doesn’t have any direct support for localization, however many people run Hugo with a variety of different languages without issues.
What doesn’t work
Sections us a naive pluralization class. We really need to abandon it and allow the end user to provide plural & singular like we do for taxonomies.
Go dates don’t have support for word renderings other than English today. Hugo inherits this limitation.
What works
Full unicode support…everywhere.
Fully configurable Urls.
Super flexible metadata and path structure
Numeric rendering of dates works regardless of language.
RSS support for different languages (even multiple languages per site).
As far as I’m aware other than the two limitations mentioned, it’s very easy and straightforward to make a multilingual site in Hugo. One of the limitations will be removed soon. The other likely won’t be fixed anytime soon, though it’s fairly easy to work around.
Hugo itself doesn’t provide any explicit multilingual capabilities, but provides one all the tools that they would need to build a multilingual site.