What strikes me as weird about this is that our intent is to do something to the array of strings, so we are looking for a function that takes this array and transforms it into something else. But we are obligated to invert our intuition here, and write this as if we are doing something to the punctuation that we want to insert between the array elements. It’s backwards, and causes us (me, anyway) to keep forgetting how to use this method. I must have gotten this wrong a dozen times. The sensible way would be something like join(array, separator). That is straightforward, and would be hard to get wrong. It could even be written in a way where the order of arguments didn’t matter, so you wouldn’t even have to remember that. Why is the separator privileged as the implicit first argument of `join`?

I accept that you’ve identified some advantages of the Python version; it’s always possible to find cases where object.method() notation gets you something.