I reported spammers ~5 times to GH, and every time the account went down in a couple of hours. Obviously mileage may vary, but I don't want the whole HN to think this process is completely broken.
I did report email spam to GH, and both got reply for them and seen their page go 404.
It was years ago though. Since I've enabled "hide my email" setting, and set that GH-generated email to my git config, "try my project" spam ceased to be an issue.
Please keep reporting spammers, usually it works.