"Vetted" is a bit of an exageration (its pretty easy to get an account. Sure technically there is a process, but its an easy one).

Basically you can't openly be evil, and if someone discovers that somebody is being evil they get kicked out. Also i think there is a proxy so you can't easily collect ip addresses.

So its a step above some random website, but ultimately its closer to a third party site then it is to being real wikipedia.

Given you are all on hackernews which is basically a link aggregator for random websites, there is really no reason for this to give anyone pause.