There are two classes of users: normal people who want to use your service and people who actively weaponize it for their own ego. Those latter users have all the time in world and can defeat any attempt to stop them. This is because, online, time is the only resource that matters. You have a limited amount of this resource. Your company has a limited amount of this resource. Your normal users have a limited amount o…
Facebook and twitter _encourage_ people to abuse their platform, that's why you can write 100 tweets from one account on a single day and they don't try to stop you at all, they know all that content will show up in their statistics, it will also make other users reply to those comments and so on; so in the end they have all incentives to keep their platform filled with people enraged with each other.
>If a small group of dedicated people wanted to ruin Hacker News for the rest of us, I have no doubt in my mind that they could.
I'm not so sure, unlike Facebook HN is not a for-profit (Ycombinator is, Hacker news is not) so something as simple as only allowing comments from user accounts created before the attack started would mitigate the problem until a better solution is slowly deployed.
Also, Facebook cannot ban an IP because other non-attacking users may be using that very same IP, a little site like HN loses nothing by banning offending IPs, a site like Facebook would get a gigantic backlash that would hurt the bottom line: Their valuation.