A non-breaking space (character 0xA0 or ALT+Space on Mac keyboard) typed into a source text is always replaced by a simple space. While this seems a good idea for any place where c++ expects white space (and cannot handle a nbsp) this also happens in string literals, like char* z=" "; (with a nbsp between " and "). This modifies behavior of the resulting program. This also happens if the code snippet is pasted in from the clipboard. This is a problem because you cannot tell by a look at the source whether it is a nbsp or a simple space.

Minimal example of the issue:

#include <QTextDocument>

int main()
{
    QString text (QChar::Nbsp);
    QTextDocument doc(text);
    QString plainText = doc.toPlainText();

    return plainText != text;
}