Custom character map doesn't work for XML+XSL format
If you have performed an override on mapentrysets.xml for another output format in order to map one character to another, and you switch to the XML format, you'll find that your common override in the Shared directory doesn't work. This is because the XML parser has slightly different character requirements (specifically, no named entities). So, perform the same override on the mapentrysets.xml file located here: Formats/XML+XSL/Transforms/
You'll need to copy and modify that file, rather than simply copying your existing file into that location. Once you have added your new entries, save the file and regenerate output to apply the changes.