My opinion is if they have more to lose than to gain from scamming me then I "trust" them. I also make sure they're within their normal trading patterns and if it's odd I don't do the deal or force another result like MM.
Just needs a restriction to one topic per section unless accounts (but thats if you sell like me nmz acc) and i want to sell a main for example i would make another post.
Doesn't need anything else.