I have always been frustrated by "traditional" wikis that intersperse random bits of discussion with the article. No one really seems to know where to discuss something. The threading is horrible.
I am very glad that Wikipedia realized that you need to separate discussion about an article from a single, authoritative, neutral article. They are two very different needs, and trying to mix them into one just doesn't work.
And for things like c2, I'd consider the lack of threading an advantage. For lots of technical discussions, this leads to clarifications that are hidden somewhere deep in that thread pile and would require an editor to factor those out in the main article. Which works fine with something that has a huge user base or paid people to work on it (i.e. Wikipedia or corp "wikis"), but not for everything.