Privacy is choice. We have a choice. I choose what to post and how to post it on this site. That isn't my question. I really want to understand the mindset behind creating an account and then answering questions only for them to be deleted in a few days.

If done selectively this seems like a good idea. Lets say there is some somewhat sensitive topic that I don't want to be archived for all time. I can use the auto delete thing. But if all of my comments or most of them I want deleted wouldn't posting with @anon make more sense?

I pretty regularly search SN for questions and comments. Finding a post with a ton of deleted comments is rather annoying. I also have noticed over the years that people get on bandwagons and just start doing what others suggest without thinking about it for themselves and their actual situations. People do this with privacy. They get scared and start doing many things that make no difference in their life but ignore other thing that would make a big impact. I wonder if that is what is going on here.