Hello Kulttuuri! I am translating this extension as we speak, but there are some problems. For messages like this one and this one, you have the action as a parameter inside a sentence, that doesn't work well with translations. For this specific message there are two actions: In Norwegian the translations would be "$1 har løst et innlegg i emnet $3" and "$1 har åpnet et innlegg i emnet $3 på nytt" (rough direct translation: "$1 has opened a post in the topic $3 again"). As you can see, the translation for the second action would be around the parameter $3, so it doesn't work. What you need to do is create separate messages for each of those cases.
Also, I noticed several messages that had mismatched parameters, for example $3 was used for both target page and reason in this one. There were more cases, so please check them thoroughly.