code: protected void isTextWellFormed(Text node) {
          // Does the data valid XML character data        
      	Character invalidChar = isWFXMLChar(node.getData());
      	if (invalidChar != null) {
              String msg =
                  Utils.messages.createMessage(
                      MsgKey.ER_WF_INVALID_CHARACTER_IN_TEXT,
                      new Object[] { Integer.toHexString(Character.getNumericValue(invalidChar.charValue())) });
  
              if (fErrorHandler != null) {
                  fErrorHandler.handleError(
                      new DOMErrorImpl(
                          DOMError.SEVERITY_FATAL_ERROR,
                          msg,
                          MsgKey.ER_WF_INVALID_CHARACTER,
                          null,
                          null,
                          null));
              }
          }
      }
docs: Checks if an Text node is well-formed, by checking if it contains invalid
  XML characters.
  
  @param data The contents of the comment node