maybe instead of putting your vouch, people can go on you profile and submit a vouch, and you can accept or not accept to add it, that way people aren't putting fake vouches no one actually said.
Maybe if we combine my idea and your idea it would be good.
Read my "trade transaction" suggestion, then read below.
That way the buyer can submit a vouch, and include a link to the trade transaction thread or the trade thread as evidence. It's fine the way it is but I do think that this will help a bit.