By default, ZC v1.3.9 and older use ISO-8859-1 in the ENGLISH language files, and make NO specifications for the database character set. Thus, the English text content will be treated as iso-8859-1 and all your database content will be based on whatever character set is set as default in your database.
For your French text, if you wish to use a different character set for your french language files, you simply set that in your french.php file.
It's primarily a result of however you've set your files.
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