Special cookies could be set for dead users and users who enable showdead to bypass the cache. For example, one of the sites I run has about 50K pageviews/day

Special cookies could be set for dead users and users who enable showdead to bypass the cache. For example, one of the sites I run has about 50K pageviews/day by logged in users, and another 600K pageviews/day by anonymous users coming from referrals or search engines. Logged in users have similar customization options so we bypass cache for these users by detecting a cookie. Obviously going the cache route would require some changes to how things are setup, its not a turn-key solution. But the insignificant amount of changes are well worth it for most content sites, but for a user generated content site like HN it would also depend on how the TTLs and cache purging are setup.