I like the system here where you cannot downvote until a certain aging process has occurred. Granted I’m not there yet, but not being able to downvote doesn’t impede the value I find on HN.
500 karma is the threshold.
Out of curiosity, is all this stuff documented anywhere? I've been on HN for years now and I had no idea what that threshold was set at. Heck, I'm not even sure I fully understand how basic features like flagging work.