At the advanced level, I would teach about run-on sentences and how they're bad, and the class would always become tremendously confused. Finally I talked to one of the Brazilian teachers, asking why run-on sentences were such a difficult concept for my students to get.
He explained that in Brazil, long, complex, strung-together sentences are considered good writing -- that the more work they are to put together, the smarter they show the writer is, and the fact that they take more work to read is the reader's problem, not the writer's! Simple, easily digestible sentences are the mark of an uneducated writer.
So if I ever turned in a paper with sentence structure like the introduction to the Declaration, I'd probably have points taken off here in the US, yet it would be fine writing in Brazil...