There is nothing more frustrating than searching for information on old reddit threads and seeing that some useful comment that used to be there is gone because the user nuked all their comments via a script. I understand the privacy reasons but at the same time it does ruin a lot of content on sites and can force people to repost old questions to get the answers again.

I assume you would also be ok with Twitter and Facebook not allowing people to delete anything? For shame!

The authors' moral right alone should allow any content authored by them to be un-published. Ever heard of a paper being pulled?

You example of bullying is top notch but what about doxing concerns? Plenty of people delete their "content" without being bullies.