@Jeff (man, I wish I could just reply to your comment directly!): You're totally right that it's possible for great content to be swallowed inside a bad thread, and I've seen that happen. At the same time, if you force people to wade through every comment linearly, it's just as common to see great comments follow-on so far toward the bottom that almost no one perseveres long enough to see them (and by extension, a lot of people won't bother leaving that great comment as comment #200 since they know no one will see it, but they will reply late to a popular thread). In practice, that hasn't been my experience with reddit though. There's almost always a comment with either the answer to "who is that?" or the question itself with the top voted reply being the answer. So, being able to scan through the root level threads quickly makes the answer more accessible than if it were a needle in a linear haystack. I do agree that traditional threading presents a lot of friction/challenge for your average non-technical user. Yet, I think totally flat and Twitter's quasi-flattened approach sacrifices too much though. I don't have the answer, but I hope someone finds a usable middle ground some day.

In your example of scanning through the reddit thread, flattened comments wouldn't reduce the distance you have to scan. If anything, that would just remove your ability to collapse away tangents you don't care about, which means more scanning. Combined with the ability for useful threads to bubble up to the top via voting, I think threading is an absolute necessity on a site like reddit. Managing the threaded comments on my own site, where some posts get several hundred comments, I completely agree that people have... challenges... dealing with threading. A lot of my commenters reply at the wrong level or to the wrong thread entirely and that can be frustrating. Yet, I still personally loathe reading/commenting in noisy places without threading. I almost never leave a comment on a page that uses Facebook comments, for example, because discussion below the first level of replies directly to the page's content is always a disaster. Same on some Stack Overflow answers; I often abandon the comments on my own answers because the lack of threading makes it so difficult. I'd rather see us come up with a way to make threading more intuitive than abandon it for relatively flat structures. Any popular site today has far too much activity for [quasi]flat structures to bear coherently.

I'm having a hard time understanding where the mutual exclusivity is between .NET and JavaScript. Whether you use ASP.NET, Rails, or Node as your backend, the more JavaScript-centric your apps are, the less that server-side framework has any impact on what kind of client-side JavaScript you can write. Once you begin writing your UI code primarily in JavaScript, it's actually quite nice to have a very fast backend acting as an API for your client-side code to consume. I find that this emerging state of affairs marginalizes a lot of the benefits that come with platforms based on dynamic languages and accentuates the strengths of languages that are faster at runtime, like C#.