Feedback: I would put in a concise summary at the very beginning. It took me a moment to understand the scope.

There isn't any mention of what should be returned if the input string is empty. Will this not happen in this kata? If so, maybe mention that.

Should the quotes preserve leading or trailing whitespaces inside them? Or is that an edgecase that won't exist?

This looks like a fun challenge!

I do think it is awesome you went out of your way to remove the brackets just to make this more clever and shorter. Well done!

In this case he had to remove the given brackets so this actually took longer, but very clever!

you can split and select all on one variable. I like your use of sort versus max and min. Nice!