"how did the downvote-jury chosen? why are they superior? what's the rule for them to downvote? for me I just feel they are a group of jerks lurking, if you call this democratic, fuck it."
I thought this was pretty well documented. You have to have a certain number of points to get the downvote functionality. This is to prevent the exact kind of shit that you're complaining about. The people that are here for 3 months and then angst for "the gold old days", then downvote everything. I've not even been around here for that long, but I've been a member of the internet for long enough to know that communities are fluid.
You might try sending an email to: hn@ycombinator.com if you're wanting your account deleted.
To just lock yourself out, set your password to a long random string.