I've searched for a solution for this issue, the thread I came across1 and it's first comment together solved it, so the whole solution together:
<?php
add_action( 'wp_footer', 'deregister_css_js' );
add_filter( 'jetpack_implode_frontend_css', '__return_false' );
function deregister_css_js () {
wp_deregister_style( 'jetpack-subscriptions' );
wp_deregister_style( 'jetpack_css' );
}
This should do it.
(Oh, by the way: this entry was written by Peter Molnar, and originally posted on petermolnar dot net.)