Reddit Preview Button FixCSS
Some custom CSS on old.reddit.com causes the expand button to glitch out (where there's supposed to be a button, there's a gibberish image instead). This style fixes this by replacing the buttons with new button images from the Silk icon set. (https://commons.wikimedia.org/wiki/Silk_icons)
This makes Facebook a peaceful place to live by removing distractions. In particular, it disables the feed on the main page and links to marketplace, videos and gaming. Easy to adjust (e.g. to reenable some of the features).