Community Server version: 12.5 deb install
It looks like the entries in a file’s versions history is stored in the native user UI language.
In the screenshot below, the languages are en_US and pt_BR:
Not a blocking bug, It probably won’t be visible unless you have an overseas use case.
A case where this might bite a little bit is when you have a multi-ethnic office where each user chooses its natural language instead of the platform/portal default language.
I wouldn’t be able to know what operation it was if described in Japanese/Chinese/Taiwanese