Chase, can you point to a rule that explains this one? I always thought it was "After everyone had stopped breathing,..." but "... across the room after everyone stopped breathing."
If I wrote that I would have left the comma out altogether. Yes? No?
You're both writing it correctly. I should have qualified "isn't wrong" by adding that it's optional when the subordinate clause trails.
In complex structures, the comma is required when the subordinate clause precedes. The rule is the same as Comma Rule 3*, so it's seldom listed with the five necessary comma rules:
Because she practiced prodigiously, Anne seldom missed a clay pigeon.
When the subordinate clause trails (as you both point out), the comma has long been optional:
Anne seldom missed a clay pigeon because she practiced prodigiously.
However, it's not wrong:
Anne seldom missed a clay pigeon, because she practiced prodigiously.
It's a style choice much like the hotly debated serial (Oxford) comma.
*Comma Rule Number 2: A comma is necessary to separate a long introductory element before a main clause. Rule 2 holds true for both simple and complex constructions:
Even though ignorant of our culture, we must always be kind to strangers. (Simple)
Since Constance is new to our company, all of us should strive to help her. (Complex)