Ask HN: Code of Conduct in Open Source

The use of Open Source "Codes of Conduct" has been increasing in the past few years, here are some examples from today:

https://github.com/opal/opal/issues/942 https://groups.google.com/forum/#!msg/golang-nuts/sy-YcVPADjg/bcO6LAr29EIJ

Are they sufficient? What do you think they're helpful for?