thanks for your question. It seems you have an issue on two ends here:
a) The AdoScript line provided in your post does not seem to correspond to the screenshot (val: "Very Low" as input, debug statement shows a different value). Is this a typo only?
b) Encoding of characters: looking at the screenshot it seems that on operating system level, the encoding is not correct to display non-unicode characters. You can check and find out in the Microsoft Windows Control Panel -> Regional Settings -> Advanced. In case you have this AdoScript code in a file, potentially the encoding of the file is not correctly set.
We have run tests here to verify that things operate - please find attached an example library, that contains a single class with an example attribute that contains French characters (Très Faible@Moyen@Très Bien)
These attribute values are used in the example at 3 different parts of the implementation:
i) as an attribute dependent graphical visualisation (see GRAPHREP Attribute dependent Visualisation FR.leo, also in the GRAPHREP of the class): the result is that dependent on the value selected in the notebook, the graphical visualisation (in this case fill color of the object) changes
ii) notebook representation: the characters are shown correctly in the notebook
iii) script interaction: the values can be set through AdoScript (see AdoScript_SET_ATTR_VAL.asc). This script selects the object with name "BAD" and sets the value to it.
Please find enclosed also the library and example model from the screenshot.