Ask HN: Who can downvote? How does one get that privelege?
Also, does karma effect how your submissions rank?
Karma has no effect on the rank of your submission or the weight of your votes. However, average per-comment karma has a (mild) effect on the ranking of comments. Additionally, flagging has a severe effect on the ranking of submissions (negates ~10 upvotes, sufficiently-flagged submissions go [dead]). Flagging does not seem to change the ordering of comments, but too many flags make a comment go [dead]. Users that (repeatedly) make comments that get flagged [dead] tend to find themselves hellbanned.
Disclaimer: That's best to my knowledge.