Was the link on /newest or on the front page?

I think it would be helpful if usernames on the new page appeared in green not when they were created within the last week, but when they had never submitted a link that was subsequently upvoted past a threshold.

I don't know whether HN does e-mail--style spam filtering on submitted pages, but it seems like an obvious thing to try if not.

I believe there's some sort of spam-filtering on the Newest page, but a lot seems to be getting through. I think it's worsening the problem that submissions have a hard time getting seen (and really heavily depend on the vicissitudes of the first few upvotes), because when legitimate submissions are interspersed with significant spam, even fewer people bother to read the Newest page carefully.

It was on the front page. I flagged it, but just felt that nothing had really happened - there wasn't any obvious feedback.

In gact that's why I like StackOverflow. There's something about the feedback you get that makes you feel like you are contributing.

Usually some posts are marked as NSFW, if it contains objectionable content. In my experience, bad links never got to the first page at all.