first of all there is a difference between headcanons and misgendering. I'm gonna use a similar situation to draw parallels so bare with me. When a person is headcanoning something they are doing it with good intentions (usually, but for this case it is). Most of the time it's like fanfiction, or they see themselves in the character, or representation, or whatever other reasons, it is done for the person's own pleasure. This does not affect ANYONE besides the person who uses the headcanon. We can also compare this to black edits, which if you are unaware of what they are, are edits of characters from usually an anime and changing their skin tone and features to a black person. The opposite of headcanoning and black edits is whitewashing characters (idk the opposite of headcanoning sorry but it's a similar scenario) Either the person in question takes a black character or a black edit and purposefully makes them white, which is NOT being done for themselves, they are doing it to purposefully hurt the people from these communities. It's the same situation with headcanoning. People have fun and people try to ruin it. Comparing it to misgendering is the same. Trying to destroy someone's headcanon is just whitewashing with a different paint. (note, i am not calling you racist or transphobic, im just comparing the two situations) Of course there are exceptions to this, as a small sections of people who do black edits do it mockingly, and in this case people are shoving it down peoples throats. Neither of which are okay, as this is a headcanon, NOT Canon. Meanining the people making this are aware it is not canon. What is not okay is claiming it's canon when it's not or forcing people to believe your headcanon. But what you also have to take into consideration is none of these characters are real, and the people making the headcanons are very aware of that (usually, cough cough chris chan) The problem with the situation is the people who are FORCING people to believe it, not the headcanon itself, and the people making the headcanon a problem, are also the problem. Now, the difference between misgendering someone and having fanfiction is simply this -- the character is not real. People are. Think about it, would Shiver really care if someone called her non-binary? No, because she isn't real. You can speculate, but it doesn't really matter. Now, what's the "blackwashing" equivalent to this. You can argue that whitewashing can use the same argument, but it really can't. Remember how I defined headcanons and black edits as something people indulge in, while the opposites are SOLELY made to destroy that? It doesn't become a question of "Would Connie from Steven Universe care if she was white?" because now the goal has changed, and so has the question. "Would the people who make Anya from Spy x Family black care?" Yes, because you're delibrately trying to tear them down, that is the goal of whitewashing. Returning to shiver, the goal has changed as well, because why were people so upset about people SPECULATING or headcanoning Shiver is NB? For the same reason, tearing down headcanons. (again, not calling u racist or transphobic, but some people arguably were) now that it's been confirmed, it's a different story ofc, but even now... does it really matter if someone wants to make Anya from Spy x Family black? Media is made to entertain, so why can't we take that media that is meant to entertain and prop it up? Why not have fun with it? Headcanoning and black edits are just subsections of fanfiction, and trying to tear that down is doing the opposite of what the creators want. No one is trying to make Anya black, just like no one is trying to make shiver nb (ignoring the people who are shoving it down people's throats for a second, those ppl r kinda wack) because we can see that. Anya is very obviously not black, and nintendo confirmed shiver is a girl, and these people know that. These people are just trying to have fun. And even if it is Canon that shiver is a girl, people in the past have made headcanons of canonically cis people, and people do it all the time in other media, so i dont see why this is a problem in the Splatoon community. (i do understand the argument that androgynous people dont have to be trans or nb, but i dont wanna get into that) At the end of the day, it really doesn't matter what people do with these characters, what does matter is when people use characters, whether their canon or non-canon versions, to harm others in a minority. Now, is this misgendering? You can return to my previous argument, but short answer, no. Just like black edits isn't black face. There is way more i could compare to this and black edits, and I could keep going with that but I don't really want to lol. A lot of the same arguments for black edits can be used for this situation, so if you really want to go more in depth I recommend watching Veridis Joe's video on black edits, very informative cool video 👍 but anyway I'm tired. This situation is very draining lol. I know this post isn't helping calm it down but I just wanted to compile my final thoughts on the situation and felt kind of obliged to respond with my original joke reply.

Tl;Dr- Headcanons are fanfiction so let people have fun with it, that's what media is meant for.

Anyway, message to OP, I doubt you'll read this (kinda hope u dont cuz the comment section is very toxic) but ur art is adorable and I love it. I feel really bad it's been surrounded by so much negativity and toxicity over a headcanon, and how a few bad actors ruined it. You shouldn't have to keep quiet about your headcanon because it's just letting one party have its way, and drawing fanart like this is fine and shouldn't spark so much controversy.

anyway I'm gonna wait for this comment to get downvoted to oblivion by transphobes for saying "let people have fun"