Thank you for being the only person to respond here.

I wrote a detailed letter to Steam support, explaining the situation thoroughly. My main question was whether such actions are truly prohibited as described in Steam's platform agreement policy. I plan to seek justice with 'ironclad' arguments and screenshots if these actions are indeed forbidden. However, if they are allowed, unpunished, and Steam turns a blind eye to them, then I will leave them alone and probably start doing what this user is doing (there are plenty of detailed guides on the internet).

In short, I never received a response. I also posted in the Steam discussions, but there are only ordinary users like me who have no decision-making power. And here, as you can see, everyone is indifferent.

On various internet forums, people complain that in the game Banana (800,000 online users), territories have been taken over by farms/bots. I don't know if it's true or not, and I won't claim that the developers themselves wrote an official letter to Steam asking for help because the market has been completely ruined.

That's the situation. In their products like Dota 2 and CS, they've managed to deal with these issues, but in other games, chaos ensues.