I can't figure out when I should/shouldn't put a comma before "then"
Pro Writing Aid says that "then" has started to replace "and then."
I went to bed, [and] then I started dreaming.
This I understand if "then" is a replacement/shortened version of "and then," but I don't understand how to use it when its in a subordinate clause
He was quiet for a moment, then said, “I’m sorry about this. I really am.”
Why is there a comma before "then" in this instance? "then said" cannot stand alone, so, grammatically, there shouldn't be a comma there and it should read as
He was quiet for a moment then said, “I’m sorry about this. I really am.”