Discussions in forums and comment threads are difficult to follow if you try to come back later and read more (Slashdot probably being the worst). Most forum systems offer tools to help, but it's such a hassle that I tend to just read through once and never come back even if I comment myself (that's been my modus operandi on BB for years).
I have only looked in here a handful of times since it was opened as a preview a while back, and I realized that I should probably figure out if there's already a system in place before suggesting anything. Turns out that if you go back to an old thread, it remembers where you left off. And replies are offered inline below the post being replied to (like Disqus), but also chronologically with every other comment (like the old BB system).
So it seems like my big annoyances have already been covered, which is pleasingly surprising considering how every comment system and forum in existence doesn't make any sense to me (the one that did was WebEx, from quite some time ago, which acted in similar ways to this).
That said, using relatively large text, lots of white space (making everything less dense visually), and then lots of structure surrounding each individual comment isn't the greatest, IMO. Increasing that density makes it easier to understand the structure of a discussion and to read through it quickly if you want to (i.e. reddit, where of course most comments aren't actually worth reading...) With your average BBCode type forums it's hard to quickly parse each comment and you have to advance more slowly. This is better than that, but could be even better to the point of being actually really good with some tweaking.
It may be that this is more noticeable on small monitors - I have been exclusively using a 13" MBP the past four years or so, and recently hooked it up to someone's 27" monitor and was amazed at how much easier it was to read the internet. I suspect most web developers have 27"+ screens (and probably more than one), and will only test usability there and then on mobile devices.