Wow big necro... I think one of the reasons they are reluctant about a PM system is that it can open the door to harassment/scamming/other unwanted contact. Right now everything users do on here is public, except for reviews I guess (but those can only be done once per game I assume?). That makes it easier for moderation purposes.
Still, I would prefer to have the ability to direct message, so that I could contact people without them having to provide an email address, discord name, etc. (And without having to post on some random page of theirs where what I want to say isn't exactly relevant to the page itself)