It’s responsibility of the one accepting the contract to check all details, so it’s a mistake on their side to not check everything necessary and to accept the contract.
That being said, I’d like to clarify the situation since I am one of the parties involved:
I have arranged transportation of H from XK-745F to Katoa in exchange for payment. For this we setup two corresponding contracts on each LM to simulate transportation contracts since they are not yet implemented.
The reason for the mistake might have been that this process of setting up contracts became routine - in addition to that noone else was using the LM.
The reason that I once posted BUY contracts on a H gas giant was that I made a mistake myself and forgot to set the type of contract to SELL.
After the mistake we reached out to @jkomut to resolve this dispute diplomatically.
A possible improvement to the UI could be to state the creator next to the ad on the local market and highlight them. Although, right now the creator of the ad is already displayed before the ad can be accepted.
Re-evaluation of the UI from an usability perspective could reduce the amount of mistakes made, although, afterall I’d say this is rather an edge case where players work with the same type of contracts repeatedly and stop paying that much attention.
Implementation of transportation type ads might help (and would make my life so much easier, haha).
About attacks on an LM:
As far as I have observed there exist two types of reputation systems that help mitigate attacks over a LM.
The one reputation system is implemented in-game and provides a ranking for a player. Depending on the type of attack, it can reduce the attacker’s reputation, i.e. they just don’t provide their part of the contract.
The other reputation system seems to be with the community as players who are observed to not fulfill their part of a contract are often called out in the Discord or in-game chat. Respectively such an attack can reduce the attacker’s reputation “inofficially”.
Although it is hard to judge how effective these reputation systems are.
In this case it would actually backfire since if the victim of the attack does not comply with an unreasonable contract they would get a hit on their ingame reputation.