Stroke is not applied properly to complex Unicode characters.
Please check the attached example; notice where the orange stroke is painted on the second character.

package texttest;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class TextTest extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override public void start(Stage stage) {
        System.out.println(com.sun.javafx.runtime.VersionInfo.getRuntimeVersion());
        
        Text t0 = new Text("\ud800\udf02");
        Text t1 = new Text("\ud800\udf02");
        t1.setStroke(Color.DARKORANGE);
        
        VBox g = new VBox();
        g.getChildren().addAll(t0, t1);
        Scene s = new Scene(g);
        
        stage.setScene(s);
        stage.sizeToScene();
        stage.show();
    }
}