Run the code:

    @Override
    public void start(Stage stage) throws Exception {
        StackPane root = new StackPane();
        final TextField textField = new TextField();

        ToggleButton button = new ToggleButton("Display caret");
        button.setSelected(true);
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                textField.setStyle("-fx-display-caret : " + ((ToggleButton) t.getSource()).isSelected() + ";");
                System.out.println(textField.getStyle());
                textField.requestFocus();
            }
        });
        root.getChildren().add(VBoxBuilder.create().children(textField, button).spacing(50).alignment(Pos.CENTER).build());

        Scene scene = new Scene(root, 300, 300);
        stage.setScene(scene);
        stage.show();
    }

When -fx-display-caret is set to false, caret is still visible. It becomes invisible, only when focus is put by mouse.
When -fx-display-caret is set to true, caret is still invisible.

Affected tests:
graphics/api/control/TextBox_6aTest.java