I believe this is by design to prevent users from accessing links which are pure spam (the majority of dead links) and may be harmful to the user. It also prevents people from benefiting from said spam even if it's not harmful, giving an incentive not to spam.
How many current dead links are pure spam and/or harmful?
[dead] Atomix Virtual DJ Pro v8.0 (forumarabia.com)
[dead] [video] Soccer Players Need to Toughen up (youtube.com)
[dead] WTF Is An Algorithm? (nodemotion.com)
[dead] Using Nested Sass Maps for TypeSetting (elijahmanor.com)
[dead] Apple vs. Facebook: What Signals Do Industry Giants Send to the App Market (appdevelopermagazine.com)
[dead] Nokia Lumia 1520 Video Playback Review (encoding.com)
[dead] Build Your Brand By Embracing Your Personality (startupprofessionals.com)
[dead] Retail shop without a mobile app? Think again (bit.ly)
[dead] Sitemap Tips: Planning, Implementation and Optimization (imforza.com)
[dead] Success Story: Michael Arrington (TechCrunch) (wealthygorilla.com)
You can google the title and site, and most of the times you can find the original article.
I think that there are very few harmful links, but most of the [dead] articles are blogspam (just copy an article and change the background color), or spam for unrelated topics (do you want to buy real state in New Zealand?) .
I also saw a few false positives before, interesting articles in site that usually have low quality articles, or the user is hellbaned by a mistake.
If you find something interesting, you can try to contact the moderator: hn@ycombinator.com
