What you seem to be saying is that I should do an elaborate and oddly specific test to prove what I already said: that color with no shading or other processing is unaffected by the linearization/correction process.  That is what,  "The color is only unchanged at the end of the process if the Shade(color)  = color," means.  By the inherent nature of linearization and correction functions, Correct(Linearize(color)) = color. 

To be precise, you didn't say "shading."  You said "flat object (=no shader/curvature effects), flat light (= no shadows) and the render output will be the same whatever the gamma settings, as long as image gamma=render gamma."  Which seemed to say that a flat object with diffuse shading, no curvature effects, and  no cast shadows wouldn't be affected by gamma correction changes, and it will.   If what you're saying is a completely unaltered color won't be affected by gamma correction, that was exactly the clarification I was making.  So we seem to be talking at cross purposes about the same thing.

You don't need to do very specific test to prove this.   All you need to do is feed a color or image into a channel that's unaltered, like Ambient Color, and make sure it has a value of 1, like setting Ambient Value to 1, and set all other colors/values to 0.   If you want to take shading out of the equation, just take it out.  You don't need a specific light, mesh, and light position for that.

Your statement about diffuse color and diffuse value seems to be based on an expectations that seem to me personally very odd.  The relationship you seem to expect (but not find) would require two things to be true:  Diffuse (color, value) = color * Diffuse(1, value) and Diffuse (color, value) = value * Diffuse(color, 1).   I would never have assumed one of those things, let alone both, about Diffuse or almost any other node, shading or otherwise.  But I'm kind of weird, and I totally get why you or any other normal person might have made that assumption.   Combining how color value is generally described (75% grey is usually how white * 0.75 is described, even if that's not correct in sRGB space), and that both terms are called "value," does make it seem like both statements would be logical.  And I've certainly made much less logical assumptions about functional relationships.

In terms of testing and process, I suggest you ask RobynsVeil how relevant and clear my writing about my work is to the general population.  I wrote tons to her that she found opaque (to be generous to myself about their effect on her), and she codes her own shaders like I do and follows all this stuff just as well as I do.  So she's not the average artist in terms of this stuff.  If I had time, which I so don't (I really shouldn't be engaging in this discussion at all, and wouldn't have posted if I didn't admire carodan's work so much and know that he's very conversant on issues surrounding GC), I still greatly doubt that posting the details of the many, many, many tests (easily thousands of hours) I've done with lighting and shading would help anyone.  I'm not even sure this discussion will be at all relevant to carodan, and he's really up on all this stuff and this discussion isn't nearly as in depth as what you're talking about would be.  I'm sure my long posts make it seem like I just want to impress people, but really I only post to try to clear things up.  In my experience, going on about my own work doesn't clear things up for anyone.  I already post too much when I post at all. 

And on that note, I'm going to bow out of this thread and stop derailing it.  I appreciate the conversation and the time it took you.  It's been an enjoyable discussion.  If you, or anyone else for that matter, has any questions for me, please PM me (I'll be unsubscribing).   I think I've posted much, much more than my fair share here, and I appreciate people's patience so far.