I think this is spot on, when you post something to a communications platform you are publishing content. How can there be any expectation you can then un-publish it? Consider this in the context of bullying or shaming, should someone who sends me an abusive message have the ability to delete all trace of it afterwards?

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.

This indeed sucks, but it would be pretty easy to fix. Just allow your nickname to be deleted for old posts automatically. I don't think individual posts' privacy is what people are usually worried about, but the possibility of getting "doxed" when given an easy way to view all of their previous messages.

I have actually considered using these scripts on my reddit account for privacy reasons but have always been concerned about deleting some useful posts/comments I have made. I definitely would love an option to unassociate my username from posts but still leave the content up.

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.