When we resize the syntaxEditor control, the folding buttons moved. You can reproduce this isssue in your demos.
If you have an XML attribute with a string value, but the value is not fully rendered into the viewport, its color defaults to black, instead of the expected blue color.
To work this around, you can create a custom XmlTagger and override its GetTags() method. This will allow you to properly catch the string value and return it as a tag span element with its ClassificationType set to "string".