I've been thinking that these could be useful new categories. It builds on the consentual vs. unconsentual division of human-born mutants and animal=born mutants, but since the mutagen bomb victims, this is no longer so clear-cut since all those humans mutated deliberately and involuntarily. And I realized this distinction actually varies for all sorts of characters.
Voluntary mutants: Necessarily a subcategory of Deliberate mutants. Characters (usually human) who consented to mutation. Examples include Genealdo, Maxence, Hun (IDW) and Dreadmon (IDW). A voluntary mutant also deals with less baggage of having mutation imposed on them, because they went into it willingly.
Involuntary mutants: Characters who were mutated without their consent. These have usually been animals (who ordinarily cannot give consent), but the mutagen bomb victims also certainly count. Most versions of Splinter and the Turtles fall in this category, and certainly Old Hob (IDW) as well. These mutants may have mental baggage over their change, even if they were previously non-sentient animals (as is true in the case of Mondo Gecko (IDW) and Seymour Gutz (IDW)). It is also outright stated that Alopex's shelter is not just a place to feed the hungry or shelter the homeless, but a space for mutants to cope with their change if they haven't already. That mental health aspect is realistic and fascinating, and...notable.
Deliberate mutants: Mutants who were mutated intentionally, either through choice, or a deliberate act, particularly in a laboratory. These mutants can have baggage, but it also depends on the benevolent of their mutator. For instance, Leatherhead (Mirage) is a deliberate involuntary mutant, but he is loved familially by Xeinos and respected by the Utroms around him, and does not curse his mutation, considering himself part alligator, part human, and culturally Utrom.
Accidental mutants: Necessarily a subcategory of Involuntary mutants. These mutations were unplanned, with negligence involved at the most.
As for the existing categories:
Animal-born mutants: Earlier in the IDW continuity, this implied a certain lack of privilege, given it was something that animals had forced on them when they didn't have the capacity to choose.
Human-born mutants: Implies a certain privilege, justified or not, and a major point of Hob's prejudice and resentment. But by mutating thousands of humans against their will, at least in the context of the story, he rendered the animal-born and human-born distinction far more moot than it ever was before.
As a matter of sociology, these are all fascinating distinctions. But there's at least one grey area:
Did Spike (2012 TV series) mutate voluntarily or involuntary? Was it accidental or deliberate? The spilling of the canister was accidental, but the story seemingly implied that Spike may have seized the opportunity to join Raphael's world, as also evidenced by Slash's recollection of distinct thoughts and feelings (and even ninja training) from before he mutated. If you think Spike was not capable of deciding such a thing, this is involuntary and accidental. If you think Spike did it on purpose, it was both voluntary and deliberate. If there is serious doubt about which, he could be left out of all of these categories, though I'm inclined to lean towards it being voluntary and deliberate as something he chose. He wouldn't be the first mutant to show unusual intelligence or sentience as a non-mutant animal, as was also true of Hamato Splinter (Mirage) and Splinter (IDW). But neither Splinter was mutated deliberately or voluntarily.
All that said, I would understand if you would consider this a chore to implement. I wouldn't blame you. It's also not absolutely essential, like human-born mutants or animal-born mutants, that these categories be implemented at all. I just thought that it would complement characters with that bit of information that helps inform their character. If you have any thoughts on this, I look forward to hearing them eventually.
There is a category I'm thinking of implementing right away. "Human-only mutants", or a similar name. (I at first considered calling it "human mutants", but technically every mutant with human DNA is part human and therefore a human mutant, and the fact that the Rise Turtles are part human has actually been made a plot point that genetically relates them to their dad.) The current problem is, these human-only mutants have been categorized in Category:Non-animal mutants, which ambiguously has also been the category or parent category for mutants based on plants, food items, etc. I mean, it can be superficially deemed that plants are "not animals," and that humans are "not animals," so they have that in common, but what do plants and humans actually have more in common with one another that they don't have with animals? Nothing, really, especially considering that humans actually are animals, by virtue of being hominids, apes, primates, mammals and vertebrates. So I think I'll start Category:Human-only mutants, as a subcategory of Category:Human-born mutants.
I am now wondering exactly where to draw the line. It was important to separate human-only mutants from non-animal mutants, but it's proving not quite as simple determining what kinds of mutations can be considered human-only. Hun is a clear example, and Dale seems pretty obvious, too. But what of Ravenwood, for instance? Her mutation is absolutely drastic, and while it is not known to specifically introduce non-human traits, it allows for some extremely nonhuman abilities, above and beyond what can be considered merely superhuman.
So far the category has only the two entries. I thought the impetus for its creation was clear-cut and trivial (which is why I felt confident acting unilaterally), but...now I'm not 100% sure. If you want to delete, reorganize, restructure it or return to the previous status quo for now, I would understand.
As for the original purpose of this thread—voluntary, involuntary, deliberate and accidental mutants—I still very much think they are viable category concepts, as they revolves around intent and consent which seems easier to determine than the finer points of distinguishing human-only vs. non-animal mutations.