Here's what I believe to be true, and I strongly suggest people agree:

Fan_characters are characters that are made, by a separate author/creator, to have an intended affiliation to an existing creation that originated from another author/creator. I.e., Kuroodod's fursona (by Kuroodod), and Mae (by Paige, yes I used someone's valid example).

Original characters are standalone creations that have no intended affiliation with any other creation. I.e., Kalnareff (by Kalnareff), and Shane Panther (by Adam Wan).

See, for Kuroodod's fursona, it is generally depicted as a Pokémon, therefore a fan character. Same with Mae, who is depicted to have been from, and inspired by, Guild Wars.

Shane Panther and Kalnareff, however, are characters who are, like I said, standalone. This is intentional and they have no affiliation with any other creation. (There are exceptions, if either is depicted to be in someone else's creation, they are still technically original characters because they are not created to have been in that relation. Take Kalnareff for example, the character interacts with pokemon in various pictures, it does not make him a fan_character because he is a separate creation. Interactions do not make someone a fan_character, but their personality/looks/story do.)

My suggestion: People just admit that their character is either original or fan.

There are those who say their fan_character is an original_character. This is a misconception that has been made, which is o.k.. The truth is that, yes, it is an original character, but not an original_character. Yes, you made it, but it is not from an original anything. It is an original, CREATION, but not from an original, independent source.

Here is a good example: Let's say I made a Pokémon named Luke the Lucario (tbh there are so many fucking 'luke the lucarios' it's driving me insane), it is a Pokémon, made from the Pokémon story. This means Luke is a fan_character. Yes, he could be my sole creation, but he is not completely standalone and original.

But let's say, instead, I made a character called Vace, (made it up off the top of my head so I don't if there is someone else named Vace but regardless...), Vace is a fox anthromorph that has no affiliation with any other story, he is my sole creation and my own character that I made. Which would make him an original_character.

One last topic to discuss is "inspiration". Inspiration does not always make a character an original or fan character. If 'Vace' was inspired by one/multiple stories, it would not make him a fan character if I made him standalone. Like let's say if Vace had a robotic eye, or he was a hitman. Those two things could be inspired by something, but it is not intentionally having to do with someone else's creation. (One exception is if there is a story-specific item, i.e. the Vorpal Sword from the live action Alice in Wonderland, then that would make him a fan_character if it is his signature weapon. If it is referenced that he had the sword or used it at one point it does not make him a fan character. Like Wonder Woman from DC being able to lift Thor's hammer and using it. Vace could also just happen to be walking in Alice in Wonderland for some reason.)

If I made 'Vace' intentionally with a relation to 'Warframe' then he would be a fan_character, but he is not, so he is an original_character.

I hope this explanation helped some people.