Could be mobile safari but I still don’t see a vouch button. :(
I have 4 karma, my guess is that HN admins restrict who can vouch, which would help stem the tide of spam.
I’m not spam. If this is working as designed, I’d like anyone calling the shots at HN (if they read this) to know that I am vouching in spirit and wish I could vouch in reality. :)
Update: I’m dumb, this comment explains what I’m too lazy to search for: