Dear Harrison,
Thank you for taking the time to write on this.
I found the discussions on the nature of spacetime to be almost always discouraging, especially when I ask to focus on Minkowski's argument - length contraction - since it allows a single explanation (that does not contradict the experimental evidence) and because of that it is clear cut: if that argument is refuted it amounts to rejecting the reality of spacetime (the same applies to time dilation and the twin paradox, but their analysis is a bit more complicated). Despite that every time I explicitly ask to address this argument, every time it is ignored and other arguments are put forward. Unfortunately, this happened again - I even attached a diagram of a more visualized presentation of Minkowski's argument.
Frankly, I really do not know how to comment; at least, I hope you understand.
Best wishes,
Vesselin
P.S. In physics, the physical world is regarded as independent of reference frames (used for its description; what is described does not depend on the choice of its description). This is not debated in physics. On 2-3 occasions I witnessed almost identical reaction when non-physicists try to question it - "I have no time for exercises in philosophy of language".