This post was motivated by a FB question.
The word then is generally an adverb with the meaning "at that time" or "next." As an adverb, it does not take punctuation.
...We were then visiting friends in the Santa Barbara area.
...She then filed the paperwork with the State.
...Then I turned left at the next corner.
If it is not an adverb, "then" is a throwaway word that does not really have any meaning in the sentence. As a throwaway, it takes commas around it.
...Are you saying, then, that he is a part of your firm?
...We will talk about that a bit later, then.
Happy punctuating!
Margie