I've been using a simple left border to highlight new comments in my extension (http://hckrnews.com/about.html http://hckrnews.com/about.html), and I've found i

I've been using a simple left border to highlight new comments in my extension (http://hckrnews.com/about.html http://hckrnews.com/about.html), and I've found it works pretty well at highlighting new comments without being too obtrusive.