Grammar and style are ultimately just two ends of a spectrum. The greatest writing sin is ambiguity (including partial ambiguity due to the possibility of mishearing or similarity to common errors); improper placement of weight means having ambiguity until the reader completes the sentence.
Weight is harmed by the widespread "rule" against using the passive voice (which is as bad a rule as "said is dead"). I'd say that topic (vs comment) is most important, then agent (vs action/patient), with subject (vs predicate/object) last and thus not sensible to make rules about.