Understand though I could easily see spammers using the data and getting 500 really should not take more than a month if you post a handful of comments a day; for example: 25 days, 5 comments a day, average of 4 upvotes per comment.
Worth noting with a rep of 500+ HN users are able to downvote comments.
Yeah, and I think the karma system works well overall. It isn't ideal for people that are significantly more consumer than producer of content, but I would guess that is the minority.
I feel there are a lot more consumers than you might imagine, myself included. I'm on HN constantly but I rarely ever comment. The karma system is not for everyone.
I think there are a few people with > 500 karma, more with an account but less karma, and even more without an account.
Pareto principle and all.
I'm not sure why that information would be valuable to spammers. It would only tell them that their posts are being flagged, but it wouldn't really help them get to the front page.
From the point a spammer is identify until their interaction with the system becomes a burden to deal with, it's better to not let them know it's known they a spammer. Craigslist does this by "ghosting" postings that's flagged as spam; that is the spammer sees the posting as live, maybe even gets an automated reply to see how/if they respond, but the general public does not see the posting.