826. Never use a comma to indicate a slight pause.
Wrong. Through the window, jumped the cat.
Right. Through the window jumped the cat.
827. Never use a comma before that, what, how, why, etc., in indirect discourse.
He said that he would go tomorrow.
He asked me what I was going to do.
She inquired how they were to go.
They asked why their salaries had been decreased.
828. Never use a comma between main clauses not joined by a conjunction; use a period. ([See 380.])