why does Mulder wear a wedding ring (series 6)

My guess would be that David Duchovny was married, and had possibly gotten married recently. Either he didn't want to remove the ring, hoặc in that season they didn't notice he was still wearing it and didn't chỉnh sửa it out.

David Duchovny got married around that time and started wearing it. The location of the hiển thị also changed from Vancouver, Canada to the States as well just because he was married.