Still, I get it, it's a kind of super-vote, reserved for people with a little karma (i.e. some "skin in the game"). Out of curiosity, how'd you guys arrive at 30 for cutoff?
You'd be surprised at how different votes and flags are in effect. The upvoting system is a lot more broken than the flagging system is. People tend to upvote as a reflexive "me like" instead of a reflective "this is interesting". (That's not a criticism—it's simply the chemical reaction of the voting mechanism and human nature.) Flagging is much more reflective in practice. You can think of vouches as an experiment in seeing whether up-flagging can contribute as much value to HN as down-flagging has.
I do this for sure. I do a bit of both, using both semantics for different cases.
Thanks for the explanation. I wonder if somebody here would like to take a stab at analyzing user data to see if 30 really is the best karma for "unlocking" these powers.