Vouching works for [dead] comments and submissions, not those that are only [flagged] (but not [dead]). I believe this is what 'crazygringo is referring to.
only for comments, not stories
Also for submissions
(Maybe the karma threshold is different, but i do see it)
Karma threshold isn’t the only criteria. I’m at ~47k karma and do not have access to vouch functionality. I might be in a sort of permanent semi penalty box (which I take no issue with, not my sandbox), so take with a grain of salt.
for me it's there for [dead] stories, but not [flagged] ones