It's not about this causing issues IMO. It's just.. why? Why would '+' not be commutative? Why not throw an error? What is the use-case for "adding" '[]' and '{}'?

Or, put another way: why would a programmer want to have this "feature" instead of being notified: "hey, you're adding '[]' and '{}', that doesn't make any sense, fix that!"

Sure you can work with a language like that. But it sure doesn't feel like somebody thought all of this this through.