Perhaps one or two small changes like changing the line height and a comment de-scope button would be nice for usability.

It's important not to go down the slippery slope of adding too much functionality, in my opinion - look at Reddit, for instance. Structurally, very similar to HN, but I'd say it adds a little too much control and detail to the end user. Do I need to know a comment's exact karma rating, the ammount of users online in a subreddit? Does there need to be two different submit buttons? It goes on and on...