See this is the problem with reddit. On a site like Twitter, pissing off your power users doesn’t matter much. If anything you lighten the server load some if they leave. You have plenty of users to replace them.
On reddit, pissing off the power users means losing the unpaid volunteers keeping your site running. Sure, reddit can just reopen the sub, and probably will. But who’s going to moderate it? A sub that big needs a serious mod team. What happens if several other large subs follow them? How is reddit planning to staff all these subs? Will whoever they grab know what they’re doing? If enough mod teams resigned in one go reddit would have no way to keep the site working. Even if they find new volunteers it doesn’t mean they’ll know how to moderate a huge community.
Twitter just needs warm bodies. Reddit relies on users to run the communities. That’s the difference. Reddit is the only big site right now where a small number of users leaving angrily can cause serious structural issues for them.