https://gist.github.com/kennethrapp/7a21c0187fedd6f47e7c
highlights lines beginning with ">", which helps differentiating quoted replies from comment text. And yes, the idea comes from imageboards, but a lot of people on HN use that syntax in their comments.
https://gist.github.com/kennethrapp/5b5e413220afb93c9c93
removes fading from downvoted and dead comments and text posts.