but it's beautiful of list monad ;)

If you consider it acceptable to not keep original order, there'd be no wrong answer.

It is generally taken as a good thing not to swap identical ( up to case-insensitivity ) elements.

Not saying this isn't an issue, but if it hasn't been fixed in four years, it's unlikely to be fixed at any time. Closing.

(>>=) is concatMap. Does it make the code more readable? No.

Sure does! Upvotes on your quality solutions is one of the best ways to earn honor, it's 1 honor for each upvote.

What a beautiful way to use list monad

Let me know tomorrow if you haven't found it and I'll help you find it.

Where is reverse in my code?

Try without reverse - like the kata suggests - it gets much trickier!

Also working submission test cases

Make it so that features show sorted by upvote value

Maybe he has skipped some katas and wants to redo them.
It would should be simple to get implemented so why not?