It's not just Japanese which has this issue. I think the following mods are affected:
Japanese
Imperial
Munchy
Nihilirian
None of the maps, tilesets or scenarios are affected, though.
Is there a quicker way to verify this than by re-downloading all the mods?
Another issue I came across is that, when you have a mod installed that is only available locally (not found on the server), it should not be updateable in the first place, so the message you get when you have selected such an entry and clicked on 'install' should be that it's not available on the server, not that you already have the newest version installed. And its icon should not change from a question mark to a green tick after this check was performed.
Finally, I don't like the unhappy smiley so much in the context it is currently used in, namely newly available mods. Newly available mods are something positive, something you want to work on because it's good, and should come with a positive icon. I think a 'star' icon or an arrow symbol pointing upwards would be great there.