I'm tired for scrolling page to find a new comment and don't like "Recent actions". So, I wrote a userscript, which adds a "new comments navigate buttons" in the right of the window.
It works in Firefox (you need GreaseMonkey plugin) and Chrome. It also should work in Opera and some other browsers - I don't use any specific API.
You can report bugs, ideas and suggestions here.
UPD: now you can view parent comment if you hover over the "^" link. This link still works.
UPD2: repository on GitHub is available.