Both PlayCatan and your mobile app have a UI that allows for counter trades (2:1 and 3:1, as well).
The trading interface on Catan Universe is, unfortunately, atrocious. I believe everyone outside of USM/exozet would agree or mostly agree with this statement. And the "Trading preferences" option is next to useless. Actually, it can be used against you by your opponents as they can automatically ask you for an arm and a leg for what they absolutely know you need. And of course, preferences change from roll to roll depending on the resources you have in your hand, the ones you gain with each roll of the dice and the ones you use during your turn. So it's actually a pain in the ass to continually having to update your trade preferences. And it keeps you from making moves promptly (i.e. delay the game).
@administrators, you mentioned in another thread that you were thinking of adapting the Catan Universe trading platform to the mobile version you are currently developing. Say it isn't so, please. This is a huge step backwards. Catan Universe should be using the trading platform in the current mobile app and adapting it to Catan Universe. Not the other way around.
Regarding official Catan Rules for domestic trade, they say this: On your turn, you can trade resource cards with any of the other players. You can announce which resources you need and what you are willing to trade for them. The other players can also make their own proposal and countertrades.
In other words, if the trading interface does not allow countertrades, as it currently does not in CU, it is not Catan. So, I'm not sure you should be advertising as "Faithful to the original version of the board game “Catan”" on Steam.
Fixing this terrible trading interface should be a top priority on your to-do list regarding game-play issues.