I agree many of the class names are well-chosen. But maybe they're not fine for every application. And Twitter may change them between versions (as they already

I agree many of the class names are well-chosen. But maybe they're not fine for every application. And Twitter may change them between versions (as they already have). The point is not to completely avoid using their naming scheme - the point is to avoid unnecessarily depending on it throughout all your HTML files, when you can easily isolate the dependency to a single Less file. If you're using something like Less or SCSS, there is almost no need at all to depend on the class names, you can use them or not use them as you see fit. We wrote the article because a lot of people are not aware they have a choice.