I’m used to circles around circles, and suddenly this one gets a sideways triangle that when expanded changes to a down-pointing triangle (see illustration).
It’s the +/- equivalent for numbered lists, because we can’t put a circle around a number to indicate that it has child items (we tried but it looks really bad).
Does that explain it or is there something else you don’t understand about these triangles?
It’s not around the number anyway, so i figure that triangle could just be a circle and it wouldn’t make any difference. Really, it was the first time I saw it, and it puzzled me what caused the change.
If not around the number, we figured it’s more intuitive to use something familiar. The triangle is a familiar symbol that indicates something is collapsed vs expanded.
The confusion might be a personal thing? I believe a number of people use numbered lists and no one else has asked about this. If you don’t like how it looks, perhaps you can try displaying it differently with the help of user styles?