According to the specs <http://www.json.org/> String value should NOT contain double quotes (") or single backslash (\).
However, when using single or double quotes, the taglib replaces these characters by entity encoded chars.
e.g. "l'assault du château de Morgane." translates to "A l'assaut du château de Morgane."
While according to the specs it should be : \"l\'assault du château de Morgane.\"