It seems like anonymity should be more of a driving force, but seeing both good and bad social media sites with each model, I'm no longer sure anonymity either preserves or inhibits culture... it might just be orthogonal.
Self-policing can also be manipulated. You cannot rely on user-intent alone, you need some structural protection against these kinds of things. Although I don't know what the best kind is.
Just pointing out that true names didn't inoculate Facebook, which doesn't even get as far as that problematic response.
That's why I said anonymity is orthogonal--that was my main point.
For example, anonymity is easier on HN, and I prefer our comments to FB. On the other hand, I'm not typing this on 4chan. There are dozens of other examples on the spectrum. Anonymity just doesn't seem like the determining factor for culture everyone makes it out to be. Maybe it has some impact, but it seems washed out by the typical culture of the group, driven by that group's interests, style, and tolerance of (or preference for) obnoxiousness.
Tangential example of technology/community interaction: Clay Shirky's "A Group Is It's Own Worst Enemy" is a great essay on how self-policing can backfire even without external influences[0]. The overall conclusion being that the technological framework surrounding the community needs to provide the means for it to support itself not only against internal influences, but also to prevent it from harming itself.
On reddit you can see in practice how the many different subcommunities apply this self-policing in practice, and what kind of effects it has. From the echo chambers of the more extremist ones (won't name any examples to avoid provoking anyone), to examples of subreddits dying due to sloppy moderation not holding back meme-ification and shitposting (same), to communities with very clear goals that are achieved through iron-fisted moderation (usually knowledge-oriented communities like /r/AskHistorians).
I agree with you, I like the ability to create random one shot accounts to comment on something, but that’s exploitable in weird ways.