Thank you for the clarification. Brother, you ask a hard question.
Though I have had no instruction on that particular portion of the passage, I did pray about it, and will just put forth a couple thoughts:
There are only two people-groups in view here; believers and unbelievers. A true believer will never bear the mark of the beast, while every one of the reprobate will.
"Buying and selling" does not refer merely to the exchange of goods. Rather, it is a metaphor for functioning in a society. It would include not only commerce, but also employment, transportation, accommodation, services, and so forth. If these things are withheld, one would be unable to function in a society.
So, the picture is one of Christians being persecuted by the world. Throughout the millennium, Christians have always been under persecution somewhere, by either the government, and/or by society. From Christ's first advent to His second advent, every generation has seen the persecution of Christians somewhere in the world.
That is about as far as I can take it. Perhaps others will add more thoughts!
