Board Game Arena

I was playing a game of Settlers of Catan (Arena) just now and a player was responding to 2:1 trade offers with 4:1 trade offers.
Specifically, someone would offer 2 sheep for a wood, and he would counteroffer 4 sheep for a wood. This is just the sweatiest play ever and extremely poor ettiquette. It's not a board game play at all, there is literally a 0% chance anyone would ever take that trade when they can always just 4:1 himself. He is relying on a minor UI issue in the game that accepting your offer/making a similar counteroffer looks nearly identical. He is hoping someone sees their trade "accepted" and doesnt notice the 2/4 difference before clicking accept.

This behavior isn't a board game play, it would never ever happen in real life; it's trying to exploit the UI.

What you're describing is well within rules of play, that other player is not doing anything that reasonably can be moderated. If you think the UI could be improved so this kind of thing doesn't trick people then raise a suggestion explaining how. Otherwise it really is on the player to pay attention to what they are accepting (and I say this as someone who has been caught by not paying enough attention when coming back to a turn-based game).

Additionally, if you think this is a poor style of play, you can red thumb them so you won't meet them again.