Is it once your karma level hits a certain level? Are you ever able to down vote submissions?
Lastly, is there a common standard that hn readers use to determine if something should be down voted? Or is it a "relative morality" issue?
Thanks for helping me become a better hn citizen!
yes, 200 points.
> Are you ever able to down vote submissions?
No, but you can 'flag' them and if enough people flag an article it will be killed. If not enough people flag an article before it reaches 10 points it would take an editors action to kill it.
> Lastly, is there a common standard that hn readers use to determine if something should be down voted?
The official line is a bit blurry, but most people try to vote based on whether or not something contributes to the conversation rather than to express their agreement / disagreement, but plenty of people do that too and there are no hard rules about it. And even if there were those would not be enforceable.
http://ycombinator.com/newsguidelines.html
If a comment doesn't satisfy those guidelines then downvote it. Some people also downvote comments that they disagree with, but I typically avoid that tendency, and only downvote comments that come across as overly negative/critical, or are completely, obviously wrong.
There's links somewhere to guidelines. Hopefully someone more HN-savvy than I am will pop in and supply them shortly.