I guess rawgit should change its strategy: they instruct people to not link to rawgit.com but to cdn.rawgit.com when you expect heavy traffic. The thing is that you have to read their instructions, which is probably not what you see when you receive a link to them. So you share that very same link, and if you share it on HN it crosses their threshold. Maybe they could use a redirect to their cdn URLs when such threshold is crossed, reverting it when some time is passed.
Beside, the redirect or a gentle message would be cheaper than serving evil.js and evil.css.
Actually, I've tried both approaches. Redirecting does nothing to reduce excessive traffic, because nobody notices they're doing anything wrong. The traffic just keeps coming, and I keep having to redirect it, which doesn't help me at all.
Displaying an annoying message, on the other hand, gets fast results, because _everyone_ notices and complains.
Both rawgit.com and cdn.rawgit.com are completely free (the former paid for out of my own pocket, the latter generously donated by MaxCDN). I don't think it's too much to ask that a person read the prominent instructions before using this free service.
No worries at all. I'm working on improving the messaging when a URL starts triggering abuse prevention measures to hopefully avoid confusing people so much.
Beside, the redirect or a gentle message would be cheaper than serving evil.js and evil.css.