i18n folder contains subfolders: one for each language. Each subfolder contains only one file: main.php. Chat loads only main.php even if subfolder contains other files.
I suggest to load all php files located in language subfolder. It allows keep separate localization files for each plugin.
If several plugins were installed and chat loaded all php files (not only main.php), it would possible to maintain every plugin separately, without changing common file main.php.