It's a little bit better if only the comments are in Swedish but it's still annoying...
Luckily it's very rare.
Bonus point when the people who decided to use English words are also all proud of their "DDD" architecture.
Based on my experience in Norway, it is common to use English but there is also not a complete surprise to find code in Norwegian either.
I remember looking at code written by a Norwegian government agency many years ago, and asking why they used Norwegian names for functions and variables. Didn't everyone use English? The answer was that they had so much domain specific terminology that it is not only hard to find English equivalents, it was so ingrained in the business logic that they don't want to risk any confusion and legal consequences. If a function was named validateFoo, then "Foo" had a single shared understanding.
I've also experienced a similar situation in an English context where the concept is renamed on UI, while everywhere in the code it uses the old name. Then things are starting to mix with each other and then a new concept is introduced with the old name...
Fun times.