TBH I was originally thinking you'd give the user a spinner or pulldown to set it to whatever you like (either on the recents page or in settings) but then I thought that would be too complicated but maybe setting a fixed threshold is less optimal. It's possible I just dont get your trust system and am thinking it's useful where its not

Brunswick

Fancy. Okay, mostly trying to gauge how new/untrusted you meant to filter out

k00b

Daily discussion thread

saloon

That depends on what percentile of what. I dont know what the distribution looks like. I assume there are three or four groupings of scores and they aren't following a single gaussian distribution, probably at least three clumps of scores. 

If I were to try to make it algorithmic, I'd probably try to collate the ranks into 100 bins, smoothe the bins through a moving average or high order polynomial fit, then search starting at a score of zero and look for a local minimum between new/inactive users and active users, and set the threshold there.