Widget Subscriptions: Could you pass the widget_title filter?

In the subscriptions module, the widget title does not pass the ‘widget_title’ filter as it is done for WordPress default widgets

I suggest that you modify the code near line 546 in subscriptions.php (the line refers to Jetpack v2.2.5).
Replace:

echo $args['before_title'] . '<label for="subscribe-field">' . esc_attr( $instance['title'] ) . '</label>' . $args['after_title'] . "\n";

by

$title = apply_filters( 'widget_title', $title, $instance, $this->id_base ); // as done for default widgets
echo $before_title . '<label for="subscribe-field">' . esc_attr( $title ) . '</label>' . $after_title . "\n";

I also took profit of the extract($args); done at line 532

https://www.ads-software.com/extend/plugins/jetpack/