XML and UNICODE - a quarrelling couple

Obviously xml has nothing to do with x-mas...

This is my input file (UTF-8 with BOM):

<?xml version="1.0" encoding="UTF-8"?>
<saves>
<!-- is Does the prolog help for Unicode support? -->
<item>
<!-- what happens to this & that comment? -->
<name>Wäßrige lösung</name>
<info>Wenig substanz wird in viel wasser gelöst.</info>
...

This is my simple script:

// WriteXmlData-b.jsx
// Read UTF data and write it back
#target framemaker

main ();

function main () {
var oXmlSettings, xmlData, sXmlFile = "WriteXml.xml"; // file exists in same dir as this script;

$.bp(true);
xmlData = GetXMLdata (sXmlFile);
WriteXMLdata (xmlData, sXmlFile);
} // --- End main --------------------------------

function WriteXMLdata (xmlData, sXmlFile) { // =============================================
var fXmlFile;
fXmlFile = new File($.fileName.replace (/[^\\\/]+$/i , sXmlFile));

try {
fXmlFile.open("w");
fXmlFile.write(xmlData);
fXmlFile.close();
} catch (e) {
alert("" + e.message + "\nThere are problems writing the XML file!");
}
return true;
} // --- End WriteXML ----------------------------

function GetXMLdata (sXmlFile) { // =======================================================
var fXmlFile, xData;

if ((sXmlFile == null) || (sXmlFile == undefined)) {
return false;
} else {
fXmlFile = new File($.fileName.replace (/[^\\\/]+$/i , sXmlFile)); // file in script folder
}
if (fXmlFile.exists === false) {
alert ("XML file «" + sXmlFile + "» not found.");
return false;
}
fXmlFile.open("r");
try {
xData = new XML(fXmlFile.read());
fXmlFile.close();
return xData;
} catch (e) {
alert ("Read error on XML file «" + sXmlFile + "». Error:\n "+ e); fXmlFile.close();
return false;
}
} //--- end getXMLdata -----------------------------

When running this program step by step I see the internal presentation

After writing I see in the file (it is still UTF-8 with BOM):

1. Where is the prologue?
2. Why do I have Chinese characters? The strange characters actually are u4000, u07C0 and u6000.
3. What is UNICODE good for XML if it is necessary to use entities for all but the ASCII characters?