Bit of an odd question, so feel free to ignore. Only reason I'm even asking is because I cannot find **any** similar questions/answers online. I know there can be fictionkind of someone's OC, but what about someone else's **self insert**? I saw someone on Tumblr list a character as one they kin, but upon looking into the link they provided, it's actually an authors self insert. Albeit not a literal IRL version (a fictional species version), but I'm not sure if that's a **thing**?
Odd questions are the best kind! I love the interesting questions that really make you think and dig deep. (Spoiler alert: That's Rani code for "I am about to ramble for an hour and a half about the thing you just asked me about, buckle up.")
Tl;dr: It's complicated, it's theoretically possible but whether it's appropriate to frame it that way and/or be public about it is another question, regarding which I do not have a solid community consensus nor a solid enough personal opinion to really guide you on coming up with your own opinion on the subject too much. You're kind of just gonna have to come up with your own opinion on it.
Okay, so, here's the thing. This is where we start to get into a whole mess of a complicated gray area in the factkin debate where there's kind of no one right answer, or at least no community consensus I can confidently tell you is the majority opinion.
As far as whether it's possible, here's the thing: I am not, generally speaking, in the business of telling people they're wrong about their own internal, subjective experiences. Within the realm of internal, subjective identity, if you experience [x], it stands to reason it must be possible to experience [x], because if it wasn't then you wouldn't be experiencing it.
With that being said, whether it's appropriate to interact with/frame those experiences in a "this is literally who and what I am" way, especially in a public setting, when it comes to other people's self-inserts is a different question. It's a slightly less spicy version of the factkin debate, which is to say it sits close to the "definitely factkin" end of the factkin-fictionkin spectrum the middle of which makes up the inconvenient gray areas nobody likes to talk about.
I am going to assume we're talking about involuntary (ie not consciously, intentionally chosen) identity for the remainder of this post, because that's usually what people mean when they talk about kintypes and because if we're talking about voluntarily, consciously chosen identity, I think there's a lot more room to say definitively "no, it's inappropriate to intentionally form an identity as someone else/someone else's persona without their express permission."
On the one hand: When speaking of experiences that are largely involuntary, it is, in my opinion, fundamentally wrong to a) ascribe morality to involuntary things or b) dictate that you understand someone else's internal, subjective experiences better than they do. These are core principles of my morality and without them I feel like you start having a lot of problems with morality in general, so I feel like they're a solid baseline to start off of. Given that baseline, 'kin of this nature are by necessity within their bounds to exist.
The counterpoint: While the experiences themselves may be involuntary, you still have the choice of how to frame and interact with those experiences. It is possible to acknowledge the experiences you are having and understand them in ways that are not "I literally am [x]", without actually discounting their existence or importance.
However, there's a problem with that: If you accept that that is a valid argument when it comes to factkin, 'kin of sonas, etc., you accept necessarily that it is a valid argument to have with regards to other kinds of 'kin as well, and there's a dangerous history there (slippery slope is only a fallacy when you don't have literal examples of it happening before), especially when it comes to fictionkin. You open yourself up to the argument that it's inappropriate to identify as small creators' OCs, or characters of a race other than your own, or any fictional character at all.
So: How do you draw the line between "appropriate" and "inappropriate" kintypes in a satisfactory, self-consistent way? How do you decide how much of a person's selfness needs to be put into a character before they become off-limits (after all, many creators will tell you that most if not all of their characters have some amount of their own self reflected within them)? What happens when someone identifies as fictionkin of a given character for weeks, months, or even years, and only much later does it come to light that the creator considers that character a representation of themself but didn't want to talk about it publicly initially - are they then suddenly "invalid" and required to reshape their entire sense of self and identity, despite the fact that it was acceptable prior to that day and nothing about the character themself or their experiences has changed?
This is, for the record, a common problem with the arguments surrounding factkin and similar - the vast majority of them ("you can't claim to know someone else's self and identity that well" comes to mind) can reasonably be applied to other kintypes, and then you have a problem when trying to delineate when it's a valid argument and when it isn't.
So, the point against it that I have the most trouble coming up with a satisfactory counter to: the difference is that with factkin, and to a slightly lesser extent self-insert OCs, the person in question can see you. Fictional characters, bluntly, cannot have their sense of self invaded because they are not present to see it - fictionkin and fictives who are uncomfortable encountering "other yous" exist, certainly, but no one can definitively claim to be the original; all of them have the same amount of "claim" to the identity in question, and thus the only way to reasonably handle it is to demand coexistence (in the sense of "not fighting about it," not in the sense of "being forced to be in each other's presence if that's uncomfortable" - quietly blocking and ignoring is a valid form of "coexistence" here). That is, I would say, objectively not true in the case of factkin, and slightly more arguably in the case of self-insert OCs*. The original is right there to be made uncomfortable, and they do, I would say, objectively have more right to their own selfhood than anyone else does.
*The trouble with including self-insert OCs in here is that we get into the "well how much self-insert is too much self-insert to be Valid(TM)" argument again then. You get the gist by now.
...Buuuuuuuuuut then we get into the problem of "telling people to suppress their identity is inherently wrong because it harms them" and how to balance those things.
*deep breath* If it seems like I'm running in circles a bit here, you may begin to understand why I haven't taken a solid stance on factkin in general. You can probably guess at my leaning based on the biases present in my writing here, but the fact remains that there's solid points on both sides of it that I struggle to refute adequately in a way that doesn't rattle some rather important pillars of my morality. (This is, to be clear, a me problem.)
So where do we go from there?
Unfortunately, so far where I go is "case-by-case basis" and "no one objectively correct answer, only a handful of definitely incorrect ones (ie, harassing people for being factkin (or whatever adjacent thing) is definitely not the right answer)." Which is... frustratingly unhelpful, vague, and open to accidental hypocrisy, I'm aware. Personally I think it depends a lot on how the individual handles their experiences and identity, both in terms of internal understanding/framing of their own experiences and of external things like "how hard would it be for the person in question to find them and be made uncomfortable, or, gods forbid, are they actually going up to that person and telling them about it". I also think that everyone's criteria for what's appropriate on both those counts is going to be a little different, and that's probably unavoidable. I also think that frankly the first one is kind of none of my business unless the person wants to share, and shouldn't be made a requirement for being welcome in the community for anyone, so it's not actually a valid criterion to determine this on a community-wide "are they allowed to be here" level, only on a "what do I personally think of and feel about this person" level. Ultimately I generally default to the "if they're not hurting anyone or being obnoxious to the person affected by this, leave them alone" position and anything from there is personal interaction choices, not community policy choices.
So... yeah. I guarantee there's points I have not covered here, either because I didn't feel they were strong enough or I just forgot about them (or I hadn't heard them before at all). More than happy to host discussion in the notes if people want to go at it, but I'm off to bed for the night myself.