The idea that inspired this post is sort of in between the two, it's a more general idea, I haven't seen anywhere else, but then I haven't read that much in recent years so I don't know how wide spread it is.

I ended up asking the author and getting the okay, which was lovely, I was just wondering what everyone else thought about it.

If I can remember where the idea is from (if I remember that it is not mine, which I mostly did so far) my modus operandi usually was simply crediting the author in my author's notes, but since this was something that wasn't a specific spell, a specific characterisation or a specific idea, I didn't know quite how to handle it.

Thank you so much for your comment. All the comments I received so far have been really enlightening.