First, most people do not use S_A_SS syntax. They use S_C_SS, because at its most fundamental, it is working CSS with the same syntax.

From what I can discern from the Stylus website, it uses a similar approach to S_A_SS, in that it is whitespace-reliant and eschews basically everything that makes CSS work (semicolons, braces, etc.) In your article you specifically said:

When we’re writing in Stylus, we’re using the same old CSS syntax. We keep all colons, semicolons and accolades. We minimize the usage of mixins and use extends sparingly. Stylus is just the tool, not the language.

So I’m guessing there must be an alternate syntax available, otherwise that statement is hypocritical.

Now to your comment on the `&` combinator, I’m curious what Stylus can do better in this regard. In S(A|C)SS, `&` can be placed before a selector to add to the current nesting context or after a selector to add a selector fragment to the beginning of the current selector context. From what I can see, the behavior is identical between both preprocessors.