1) The Internet never forgets. If you post something regretful in a fit of rage you can never take it back. You are not the same person you were ten years ago (even if you have the same name). Do you want to be judged today on how that person behaved back then? It is naive to think you won't be judged so.
2) There are some really batsh*t-crazy people in the world. I prefer to be somewhat isolated from them.
3) How do you verify a real name from a real-sounding name?
I would also like to see some evidence that "Real Name" = "better comments".
#3 is what always confuses me about the argument that switching to real names would in and of itself make flames and trolling less common.
That said, I don't think this is necessarily something where solid evidence matters. It seems to me that requiring real names is much more about making bloggers and journalists who consistently have their real names attached to postings feel more on an even footing with their commentariat. See, for example, this post on crosscut where Ted Van Dyk argues that he feels more comfortable with a critic that has a real name attached: http://crosscut.com/blog/crosscut/19530/Should-online-commen... Is that about categorical differences in comment quality, or personal comfort within a newsroom?
I put discussion/aggregator sites like HN in a different class than news sites. We come here to talk about things we see elsewhere. It's not very important who we are in Real Life. I think anonymity can improve the discussions.
Mr. Van Dyk makes a valid point but doesn't take it to the conclusion that comments aren't created equal. I would prefer to only see comments that improve the overall quality of the article -- just like the old days when you had to write a letter to the editor to augment or rebut an article (as he mentions).
2) There are some really batsh*t-crazy people in the world. I prefer to be somewhat isolated from them.
3) How do you verify a real name from a real-sounding name?
I would also like to see some evidence that "Real Name" = "better comments".