Does this feature work for anyone? Since the game was released neither myself nor my friends have been able to trade these currencies. Regardless of the slider position both values remain at -1.

It isn't Gold <-> Gem Exchange, it's buying
[real money] -> [Gems (Crystals)] -> [game gold, amulets, equipment, emotions, painting, etc]

Thanks for explaining - I misunderstood the system. It sucks that you cannot trade both ways. If you could convert gold into gems it would probably alleviate many people's pay to win concerns.

And leave Devs without money.

If they made it so that its costs like, 200 gold for 1 gem, then only premium accounts would really be able to get that kind of money.
Non-premium accounts take forever to accumulate that much, and then it is only one gem.

There is a HUGE gold surplus on top level. With such exchange as you suggesting, you can save for premium easily, then take x2.5 bonus to gold from it, and then you can afford everything without actually paying a dime.
Sure it would be cool to play the game like that, but it will never happen.