Real name policies may (or may not) foster civil discourse, but they do so in a way that favors the already privileged. It's a burden for marginalized people and a barrier to them resolving their issues.

I was molested as a child and women generally tend to have less agency over their lives than men. When I first got online, I used my real first name and last name. I eventually moved to middle name and place as my default semi anonymous handle for privacy reasons because my first name plus last name is so distinctive. I'm back to using my full name online, though my handle in most places is first name plus middle name.

It was a long journey of getting there. It included a divorce, figuring out how to talk publicly -- which I think men tend to get inculcated with early and women don't -- and assorted other factors.

The perfect is the enemy of the good. If you only want civil discourse in your space and that's all that matters to you, you can achieve that by limiting it to very privileged people with no serious personal problems. Insisting on real names is a polite means to exclude anyone for whom speaking publicly under their real name might be a problem, so I'm sure it can help keep things superficially civil in your little corner of the universe.

I am also sure it helps further narrow the lives of people with already narrow existences by ever so politely silencing them online in ways they are already silenced offline. Which isn't actually all that kind, imo.