I'm going to try to break this down post by post.
First, thanks to both
@Globin347 and
@BlackZero for the explanations on the fourth dimension. I had the basic idea of being unable to perceive its fourth dimension, but I could not explain it for the life of me. So, from what I understand, the ink is four-dimensional (it exists in five dimensions) which allows for solid, three-dimensional objects to slip into the space created by the extra dimension, but not everything. Would it be based on how integrated the ink is within the object in question? Since the inklings' cells likely have ink as a fluid matrix, this could explain how inklings (and other ink related creatures/objects) can use the fourth dimension at will without it being one of their physical dimensions.
From continuing to read through the thread, I completely agree on the existence of a splat reflex. It would allow the inkling to evade a predator and keep its harder to replace organs intact. I also agree that the spawn point helps to speed up the process of reforming the body. I much prefer this over recreating a deceased inkling from scratch as that would also require the transferring of years of experience to the new inkling. Where I start to question things is the "soul". It very well could be the major organs compacted into a small space with the ink being four-dimensional, but I would like to at least try to explain the floating. What if part of the splat reflex was to pressurize ink within the body cavity, or even use the pressure within the hydrostatic skeleton (if there is one), to propel the "soul" to a safer place? It would be similar to the propulsion system used in the real life flying squids or in-game super jumps. The "soul" would then travel to the spawn point to recollect the scattered parts of its body or use organic material within the spawn point to recreate a body. Ink itself is already organic, so why not give it a cellular component?
What I am proposing for the way that ink splats inklings is an enzyme. It acts on a specific substrate, likely collagen in this case, and wither destroys or, more likely, denatures it (if it is denatured, it could be repaired when the body reforms). Normally, this enzyme would run rampant and destroy any collagen it finds, even in the "host" inkling. This doesn't happen because it is allosterically inhibited by an identifier protein. Allosteric inhibition is when a molecule binds to an enzyme away from the active site to prevent the enzyme from working and can be reversed. When the color of an inkling changes, so does the identifier protein, according to what you have stated. I am also proposing that this enzyme also changes to be inhibited by the identifier protein that the inkling has. When the enzyme is with the specific identifier protein, the protein binds to the enzyme to prevent it from denaturing the collagen. With an enemy inkling, the correct identifier protein would be missing and the enzyme would proceed to denature the collagen. To answer your question, it should not "burn" a human, but since the human would most likely lack the identifier protein, any collagen present would be destroyed. Since collagen is about 30-40% of our bodies' protein, the results would still be disastrous, likely killing the human. (Say goodbye to your young-looking skin and functioning joints.)
To expand on the paragraph above, the enzyme would have to be present in the ink without the identifier protein. Thus, the protein would likely exist in the skin. It would also likely be a signal to produce a certain kind of ink enzyme to allow for the offensive properties that are exhibited. The enzymes for each ink color would be very similar to each other so that it wouldn't require a new enzyme to be made and instead could just be switched to a different enzyme. This may also explain why they wait until a certain age to participate in battles, biologically at least. Their bodies could need time to mature to the point where the necessary proteins can be made quickly enough to battle for long periods of time.
On the point of rapid evolution, I completely agree. It was likely a misunderstanding of the effects of nuclear radiation on mutation and evolution. Although, it
could be possible for the inklings to evolve in that time period if their reproductive rate increased dramatically at some point, slowing down again later. It would be the same effect that bacteria experience. Since they reproduce so quickly, genetic mutations compound rapidly and produce rapid evolution, such as antibiotic resistance. Still
highly unlikely, but it takes out the excuse that writers simply didn't know what they were doing.
If I didn't answer anything, just tell me. Feel free to poke holes in any and all of this.
