Bit of advice from me personally.

People change, Vouches Remain

Add that to you quote books init

By that i basically mean, if a trade was done lets say 2 years ago that user still has that vouch, the user might be more trustworthy, however they might have changed to become a scammer, i reccomend you put a cut-off point on vouches you see. normally i reccomend 2-3 months at most.