The "contact the editor" goes back to the beginning of the ODP, long before any ODP forum. The web social environment is very different now; as a class, ODP submitters are very different from the "independent contributors" who helped the ODP become the dominant web directoryl spam-type abuses are close to killing off any open communication setups on the web. I'm not sure that, in the current environment, in the current form, the "contact an editor" has any possible use for a submitter.
For an editor or for someone interested in a particular topic, it may be a way of making contact with people who are interested in the same subjects (like contact information on any other noncommercial website): I've had a few e-mails from that motive.