Both forms are valid according to ISO 31-11. Your form is often called the "French notation" and I assume used more commonly in France and countries with French influences.

Nope, I learned [closed, open) in school and .. vs ... in ruby. Python range() is [closed, open) so that's what I use everywhere now.

I'm from the US and I was taught the way it is in the article title. Can't say I've ever seen that before.

It's an interesting notation, but I feel like if I encountered it out in the wild I might assume it was a typo if it was only on one side. (IE: If I saw `[100, 200[` I would think they meant `[100, 200]`)

Yes I did. In Belgium in the 80's and 90's. But on Internet, I mostly see [a,b) instead of [a,b[