[Jetpack] Remove all CSS.

plugin.php

<?php

// First, make sure Jetpack doesn't concatenate all its CSS
add_filter( 'jetpack_implode_frontend_css', '__return_false' );

// Then, remove each CSS file, one at a time
// You probably won't need them all, unless you use all the modules, and all the themes! :)
// Some of these are also only loaded on specific admin pages, so it wouldn't affect your readers
function jeherve_remove_all_jp_css() {
        wp_deregister_style( 'AtD_style' );                    // After the Deadline
        wp_deregister_style( 'jetpack_likes' );                // Likes
        wp_deregister_style( 'jetpack_related-posts' );        // Related Posts
        wp_deregister_style( 'jetpack-carousel' );             // Carousel
        wp_deregister_style( 'grunion.css' );                  // Contact form
        wp_deregister_style( 'the-neverending-homepage' );     // Infinite Scroll
        wp_deregister_style( 'infinity-twentyten' );           // Infinite Scroll - Twenty Ten
        wp_deregister_style( 'infinity-twentyeleven' );        // Infinite Scroll - Twenty Eleven
        wp_deregister_style( 'infinity-twentytwelve' );        // Infinite Scroll - Twenty Twelve
        wp_deregister_style( 'infinity-twentythirteen' );      // Infinite Scroll - Twenty Thirteen
        wp_deregister_style( 'infinity-twentyfourteen' );      // Infinite Scroll - Twenty Fourteen
        wp_deregister_style( 'infinity-twentyfifteen' );       // Infinite Scroll - Twenty Fifteen
        wp_deregister_style( 'noticons' );                     // Notes
        wp_deregister_style( 'post-by-email' );                // Post by Email
        wp_deregister_style( 'publicize' );                    // Publicize
        wp_deregister_style( 'sharedaddy' );                   // Sharing
        wp_deregister_style( 'sharing' );                      // Sharing
        wp_deregister_style( 'stats_reports_css' );            // Stats
        wp_deregister_style( 'jetpack-widgets' );              // Widgets
        wp_deregister_style( 'jetpack-slideshow' );            // Slideshows
        wp_deregister_style( 'presentations' );                // Presentation shortcode
        wp_deregister_style( 'jetpack-subscriptions' );        // Subscriptions
        wp_deregister_style( 'tiled-gallery' );                // Tiled Galleries
        wp_deregister_style( 'widget-conditions' );            // Widget Visibility
        wp_deregister_style( 'jetpack_display_posts_widget' ); // Display Posts Widget
        wp_deregister_style( 'gravatar-profile-widget' );      // Gravatar Widget
        wp_deregister_style( 'widget-grid-and-list' );         // Top Posts widget
        wp_deregister_style( 'jetpack-widgets' );              // Widgets
}
add_action( 'wp_enqueue_scripts', 'jeherve_remove_all_jp_css' );

Is this solution still valid? I'm trying to dequeue both style and scripts for the slideshow, but without success... also tried with TwentyFifteen, but nothing seems to work. TIA

It works but not for all styles, ie:
Related Posts: YES
Sharedaddy: NO

Any idea why?

For Sharedaddy / Sharing, I'd guess it's because they give users a UI control for including the CSS & JS

I'd love to know how to get rid of the Jetpack Image Widget CSS.

Just revisited this issue the other day and came up with this:

wp_deregister_style( 'jetpack_image_widget' ); // Image Widgets
wp_dequeue_style( 'jetpack_image_widget' );

Seems to work on my local install.

Worked a treat – thank you kindly.