You've invented a new medical hazard, which makes no sense whatsoever. If you were to somehow introduce enough solid matter into your blood that it lowers your RBC count on a volumetric basis, then you'd have far bigger problems than oxygen transport in general. And at that point, it wouldn't matter what the material is.
And you still haven't answered the question: how do you imagine such a large amount of powdered PTFE would get into your body? PTFE can't be digested, and there's no evidence that it's passed to the blood stream though inhalation. Are you really afraid that someone's going to inject you with a specially formulated suspension of ultra-fine PTFE?
The rest of your post is a bunch of mumbo jumbo.
> injuries produce stressor signals when the body is damaged and bleeding (since the lowered blood pressure decreases the efficiency of the heart's ability to deliver oxygen)
Not sure what "signals" you think you're talking about, but our compensation for traumatic hypovolemia is triggered by vascular baroreceptors, a mechanism has nothing to do with the effect of foreign particles in our blood.
> Keeping your blood clean of impurities is traditionally (mostly) handled by the kidneys, if some PTFE is introduced into the blood stream does PTFE recognize this impurity as a dilution - will it properly filter it out?
No, the kidneys do not filter out solids. That's not how they work. Your body has ways to deal with foreign particles, which vary widely depending on the nature of the material -- particle size and shape, reactivity, opsonizability, etc. None of these ways involve the kidneys in any significant way.
> I don't have any evidence to the contrary...
Nor, apparently, are you able to account for the half-century of experience we have in using PTFE inside people's bodies. Nor as well the material's track record in a huge variety of other applications. E.g., nearly every household in the first world has used PTFE-coated non-stick cookware. The fact that we have no evidence of PTFE somehow entering people's bloodstream and "diluting" their blood might clue you in to the plausibility of your theory. Or maybe not.
> ...but I am skeptical of how conclusive the supporting evidence is and would place the onus on proving harmlessness rather than harmfulness.
You can say that about anything. Literally anything.
Honestly, I know you think you're discussing a complex topic with some sort of clever reasoning, but it's only because you're missing a lot of basic knowledge of chemistry and physiology. I think I need to be done with this now.