But you wrote:
"The idea being that defining it as inherently supernatural is impossible and simply a linguistic reshuffling, when it's really more like "you've simply started calling your belief system something else, but it's actually still just Christian.""
Where you effectively claim that "Christian religion" can be one where somebody is even one who doesn't believe in supernatural. Because... some other values count too?
Can really somebody who doesn't believe that Jesus is a "Christ" (the anointed one, a "Messiah", it's not a surname but the specific role in the universe of believers) be a Christian? And somebody who doesn't believe in any supernatural deity at all?
I for example admit I grew up in the area where traditionally most of the inhabitants were real Christian believers, but I surely am not a Christian. The Church would surely not accept that claim.
Edit: user
keiferski answers below that to him "it's unclear what "supernatural" means in this context." Let me write that even more clearly: I don't believe in the existence of any supernatural deity, i.e. one which can influence the events on Earth that occur among humans or one which can "change the rules" how the universe functions, as established by the scientific experiments and research. I also define the belief in life after death as a belief in supernatural, and I assert that I don't have that belief. Also, the area I grew up was never inhabited by majority of "protestants." I was also never in life an object of any religious ceremony (and I consider myself lucky for growing up in such an environment, learning how most of people in the U.S. live). Most of the people I know who were baptized as children later officially renounced the Church, and the Church wiped them out of its records. All of them never went to any religious school, just state schools (some of them had a subject where they explicitly learned about religion though). People I knew who already died don't have any religious sign on their graves, and didn't believe they will "live" after their death. People who live together with their partners and even have children didn't even officially register in the state institutions, and they even less had any ceremony in any church. It's not "complicated" at all. And I'm not even some special exception -- exactly because not every area in the western world functions like an average "contemporary American" would expect. What is that that those people in my environment and I "do" which you believe could make us "Christians" then? (I also admit I know a few people in the circle of people around me, a very small minority, who do say they believe in Jesus Christ and that they have Christian morale, and attempt to behave according to that, while also not being consistent though their life. But they are a minority, and like I've said, even they don't "do" consistently what "the religion" would "expect" from them).