If I stay at the sentence level, 'grammar' is -- maybe along with vocabulary -- kind of the only game in town. Discourse-level features? Elusive.
But remember the "can able to" example and the argument that grammar is ideological:
"I didn't want to jeopardize my case for pluralizing academic writing by extending it to
the controversial terrain of grammar. But a combination of developments in theoretical discourses, social changes, communicative advances, and pedagogical rethinking (reviewed in this article) tell me that now is the time to take my position to its logical conclusion. The moment is ripe to extend my argument of pluralizing English and academic writing into the “deep structure” of grammar."
...thus saith Canagarajah (2006).